Especially in GRB, the small maps and removed markers help a lot in making up for the speed disadvantage. If you enjoy air to air too and not just CAS this is actually not a bad choice.
But yeah, for CAS it’s not nearly as good as other nations until some select lineups like the one with the Albatros (which will be changed anyways) and then top tier with the Su-30MKM. Ground also has a bit of a rough start. Not bad necessarily, but also not super amazing. Many BRs also lack lineups completely, like anything with 10.X which really hurts CAS aircraft like the A-7E that’s otherwise quite good but let down by the 9.7 and 11.3 ground lineups it needs to be used with.
I think the best tree for you would be the US tree. They have good planes and tanks at all ranks and the grind experience will probably be as enjoyable as it can be. If you want a non meta nation i would say go for Britain. This is a hot take i know. Britain forces you to adapt to their tanks and you have to play smart but overall they also have a lot of fun light and medium tanks and their aircraft are also pretty good. Fighting at a disadvantage will also make you a far better player in the long run because you really have to learn how to play. I got Britain as my second Nation and never regretted it. The choice is yours.