With a year to go until the T20 World Cup in India, England will be at full strength in a T20I series in for the first time since Jofra Archer qualified for the national team when they get underway in South Africa on Friday evening. They are unbeaten in their last seven series, and well-placed to become the first team to hold both 50-over and 20-over men's titles simultaneously, but there remain a few minor issues to iron out...

The top-order conundrum

England are overflowing with opening options. Their 50-over opening pair, Jonny Bairstow and Jason Roy, have been separated by the emergence of Jos Buttler as one of the world's most destructive T20 openers over the last two-and-a-half years. Dawid Malan - the ICC's No. 1-ranked T20I batsman - is best suited to the top three, while Ben Stokes flourished at the top of the Rajasthan Royals order in the IPL.

The likely outcome is that England will try to fit all five into their top six, with captain Eoin Morgan filling the extra spot. Despite Buttler's success in the middle order for Rajasthan, he looks certain to continue at the top, most likely alongside Roy. In their T20I series in South Africa in February, England went with Bairstow at No. 3 and split the 'spare' batting position at No. 4 or No. 5 between Malan and Joe Denly, but Bairstow's impressive record against spin and Malan's tendency to start slowly before exploding into gear could see those roles reversed.

Stokes, meanwhile, presents a headache: his record in the middle order is underwhelming, and like Malan, he tends to have a few sighters before teeing off. He batted at No. 3 in Monday's warm-up game, but is more likely to slot into the middle order with Sam Billings left on the bench. Keeping Malan at No. 3 with Bairstow at No. 4 would also avoid England having three right-handers at the top of the order followed by four left-handers in the middle, a situation which would allow top teams to create favourable match-ups by using spinners who turn the ball away from the bat throughout the innings.

Moeen Ali or Sam Curran - or both?

The area in which England have the least depth is their spin bowling. While Adil Rashid is a lock in the starting XI, his shoulder has presented some level of concern over the last 18 months, and he is the only frontline spinner in the 15-man squad, with Liam Dawson (injured) and Matt Parkinson (omitted) both absent.

Moeen Ali has been ever-present in the side this year but after being used in the Powerplay for a match-up against Quinton de Kock in February's series, he bowled only one over of offspin in each of England's five bowling innings in their home summer, and his returns with the bat have been sporadic.

England have a balancing act to strike between looking to win the series at hand and preparing for the long term, with next year's T20 World Cup in India likely to present a significantly different set of conditions to Newlands and Paarl. If they lean towards the latter, then Moeen will likely keep his spot at No. 7 and share four overs with Stokes; if they go for the former, his place could well be taken by Sam Curran, whose breakthrough IPL season with Chennai Super Kings demonstrated his game-changing abilities with both bat and ball, as did his match-winning cameo in Monday's warm-up match.

They could, of course, pick both, but it would leave their balance slightly off: that would mean they either had seven bowling options and left out one of their specialist batsmen, or had to split eight overs between Moeen, Curran and Stokes. As a result, Curran may edge Moeen out.

Where does Morgan fit in with the bat?

Morgan has spent the vast majority of his T20I career at No. 4, and his sparkling recent form in the format - he averages 44.27 with a strike rate of 183.77 since May 2019 - has primarily come in that role. But his particular strength has been hitting at the death: in that timeframe, he has scored at a mind-boggling 230.76 strike rate in all T20s in the final four overs of an innings. And his explosiveness does not seem to be reliant on having set himself in the middle overs, either; his strike rate in the first 10 balls of his innings has shot up in the past couple of years, with the influence of two T10 seasons seemingly rubbing off on him.

Perhaps with that in mind, he shuffled down to No. 5 against Australia, and batted at No. 4 only twice in the IPL for Kolkata Knight Riders. Given England's wealth of top-order options, and their desire to give Stokes sufficient time to set himself, Morgan may push himself as far down as No. 6 in this series, depending on the situation in each innings. While that might mean he faces fewer balls on average than he would at No. 4 or No. 5, it should also give the top order licence to attack even more, in the knowledge that there is no shortage of batting depth.

Who are their Powerplay bowlers?

England struggled badly with the new ball in February's series, taking only one Powerplay wicket in three games with Jofra Archer missing through injury. They again lacked new-ball bite in their home series against Pakistan this summer, though Archer's success up front alongside Mark Wood against Australia in September suggested the issue might simply be down to a lack of depth.

Wood was impressive in the Powerplay in the Australia series, taking two wickets in seven overs, but has only played 11 T20Is and his record in South Africa earlier this year - 4 for 118 across ten overs - might be cause for concern. With Reece Topley, the 6ft 7in left-arm seamer, likely to start on the bench, and the injured David Willey waiting in the wings, Wood will hope that the success of 90mph/145kph bowlers in the IPL extends into this series.

England may also be tempted to give Archer three overs in the Powerplay, something that his IPL franchise Rajasthan Royals never did due to their reliance on him at the death. With at least one of his death specialists - Tom Curran and Chris Jordan - likely to play, Morgan may opt to attack with Archer early. There is little in the way of previous evidence as to how likely this is - Archer has played only four T20Is due to injuries and rotation - but it is the sort of aggressive move that Morgan will doubtless consider. If he plays, Sam Curran may also be used with the new ball, as he was in New Zealand last winter.

How will they cope with Shamsi's threat?

England may well consider it a shame that South Africa have not selected Imran Tahir for this series: they lost wickets regularly when facing Shadab Khan in the summer, and legspin will be a feature in next year's T20 World Cup. Instead, the left-arm wristspinner Tabraiz Shamsi is the main spin threat to counter over the next week, though he should not be taken lightly. As the below table shows, only two England batsmen managed to take him down in the high-scoring series earlier this year.

In particular, it will be interesting to see how England fare immediately after the Powerplay. Buttler raised that phase as a possible area for improvement earlier this month, while Malan, Morgan, Roy and Stokes will all hope to do better against Shamsi than they did last time out.

Matt Roller is an assistant editor at ESPNcricinfo. He tweets at @mroller98