MERP for sure. We had a ton of fun playing that.

I use inkscape for overland maps. I use Watabou Medieval City generator for city maps. I use Dungeon Alchemist for dungeon/indoor battlemaps.

I took a page from Flee Mortals and use actions instead of spells for NPC combatants.

https://shop.mcdmproductions.com/collections/flee-mortals-the-mcdm-monster-book

I think that main problem is lack of support for the former. Some people really like to do that, but rolling your own is hard. There are some third party supplement that might fit.

I recommend using the 4th Ed lite version (free), and using the Caravan To Ein Arris (also free).