I’ve done 2 transports before. It has its own sets of pros and cons.
The first thing to understand is that you require a bid in Africa (Libya/Algeria). You must take Egypt on G1, otherwise the UK gets a windfall of units to use against you across your underbelly, meaning you’ll make no progress in Africa whatsoever. How large the bid is depends on your confidence. It could be as low as 1 inf, and it may be as high as 1 inf 1 arm if you’re counting on losing the fighter in Ukraine.
The next in line is that you’re attempting to link the med and baltic fleets together to create a threatening navy. If you don’t do so, the carrier is a better buy if you simply want to sit there because of the immense increase in defense it presents (+9 dice points, +1 count vs 2 transports).
The third thing is that if you’re serious about threatening UK/US with those transports, you need to keep a modest number of units in W. Europe. Some people don’t do that, and sometimes you really don’t want nor need to because the landing the Allies can present early on is insignificant.
If you understand those points, then the 2 transport buy works viably. The major pro of 2 transports vs 1 carrier is that you don’t need to keep your fighters out at sea. Buying a carrier essentially does mean you create another territory you have to defend with fighters. 2 transports also gives you potentially great flexibility if the linked fleet makes it back to the med. 2 transports is also better than 1 carrier if you’re just going to suicide your navy.
There is one counter that I like as the US against a 2 tran buy. The US starts off with 2 fighter 1 car as their purchase, and moves their existing navy to SZ1. On US2, they can attack the linked fleet with 5 fighter 1 bomber 1 dest 2 tran, which has a high chance of wiping everything out there. Still, the US is set back. It has likely lost 2 of its existing transports, and has built none to compensate for it. According to my experience in a few games against myself, the results still tend towards an Allied victory, but I couldn’t tell you for sure as my style keeps changing a bit and you can never tell with some fluky dice here and there.
A carrier buy + naval link is pretty deadly. The US doesn’t have a quick counter to it, and it’s a very nasty fleet defensively. It may have not much flexibility as 2 transports and does require your fighters float out in the waters, but neither do you have to station troops in W. Europe, and it’s very likely that your fleet will live past Turn 2.