Well, there are plenty of explainers out there (particularly AndrewAAGamer’s one), and most of what applies to Global 1940 works for Europe 1940 too.
Carriers are indeed more of a Pacific thing and the cost-benefit analysis done by AndrewAAGamer does confirm that battleships and cruisers are useless.
I assume carriers are just double hit to provide some extra firepower on defense, making them more valuable and justifying their high price (I assume the price has to be high to make it more realistic when compared to other ship types). Scale means the double hit probably isn’t required in smaller versions like 1942 and 1941 to justify the cost.
Been a while since I’ve played Europe 1940 by itself, but I generally don’t put facilities down in any of the 1940 games. Many facility locations feel suited for only one plan which can easily be changed or disrupted by your opponent.
Artillery is very useful. If the US is sending forces the long route obviously tanks are better, but artillery is superior in Western Europe. For Italy, I like to buy it to provide some extra counterattacking power if they’re in “defend Fortress Europe” mode. 4 infantry and 3 artillery on the offensive is vastly superior to 8 infantry (not saying that’s a good ratio to scale up, must trying to show how effective artillery can be).
And honestly, as Germany I buy artillery because if you only buy tanks, not many of them reach their “full potential”. If I just want some extra firepower for infantry, tanks are completely wasted in that role. I could see how tanks previously being 5 IPCs might make it worth it, but I’d much rather have 3 artillery accompany my large infantry stack than 2 tanks (especially since it seems that high level players don’t make that much use of blitzing on the Eastern Front, especially in crucial stages).
I rarely buy mechanized infantry too. They’re more for if you need extra movement to have as many forces as possible for a particular, large scale plan to be executed by a certain turn (say, a German assault on Moscow). I’ve never put mechanized infantry on transports.
Sorry if this was a bit long, I didn’t have time to make it shorter.