None of which NATO countries has offered to use in Ukraine.
I think logistics by railway would be problematic if NATO allies launched a few thousand cruise missiles.
Air power is of little use if your forces don't have access to the relevant area. The Baltic states are surrounded by Russian bases and air defenses, while NATO bases are far away. Right now, Kaliningrad is effectively a fortress that separates the Baltic states from the rest of NATO. Sweden and Finland give NATO air forces the option to bypass Kaliningrad and operate from bases that are closer to the Baltic states.
But yes, Sweden and Finland in NATO is nice. Also for the fact that NATO not intervening in aggression against Sweden or Finland is hard to imagine, so getting papers on the marriage is nice for all parties involved.
Also, as far as I understand, the combat radius fighter jets is quite short. It's something like 500 to 1200 km, depending on aircraft type and weapons load. Having bases 100 or 200 km closer is already a significant advantage.
The geographic situation largely explains why the Baltic States support the NATO membership of Sweden and Finland so strongly, and why Russia is opposed to it. With Sweden and Finland in NATO, the Baltic Sea will become NATO's internal sea. NATO would likely have naval and air superiority over it, which would keep supply lines open and give them a chance to defend the Baltic States with conventional weapons.