For FE2, I would definitely recommend gTerl's excellent, various Italian map terrains (as indicated above). Also very good are Stary's enhancements to stock western front terrains in FE2 (the latter were done for FE/FEgold, but work just as well in FE2). Regarding plane mods, I suggest looking at Stephen1918's hangar - superb and rare WWI aircraft may be found there, such as the Siemens-Schuckert D.I, etc. For flight model/damage model tweaks and enhancements, as well as for flight models to several beta aircraft done by Geezer years ago and never fully completed, recommended is to check the "about me" tab under my main CombatAce profile for more info. and/or mod information. FE2, properly modded, has some of the best flight models in any WWI flight sim (including when compared with Rise of Flight).
Good flying to you,