Full Screen FPS drop

My advice is: stick to windowed mode. The game was designed a bit more than 20 years ago, on much different architecture than X64 processors and Windows 7 X64 OS (Windows 98 was the thing back then). Although using compatibility settings with Win XP Sp2 helps, this involves software and some hardware translations that happen in real time, by the millions per second.
While glide certainly helps with making graphics fluid, there are limitations. Also, summon necro, with lots of skellies and revives is one of the most graphics-demanding choice of characters in D2 (I remember also about firesorc meteor, druid fissure, assa wake of fire and there are maybe some others in this category); especially with auras from beast, merc weapon and merc himself.

Moreover, when playing windowed, you get to do muling among your chars, games with 2+ players, have a char in a sell/buy game and another actively playing and more interesting stuff, than in single full-screen mode. So, again, best stick to windowed mode.