the game starts chugging on the bigger maps on my full desktop. Its a potatoe, but damn does it chug.
The engine is not built for such big (especially tall) maps and for such long visibility distances.
Modders are aware of it, but willingly decided to use it in spite of suboptimal user experience.
1/ vanilla maps have height = 4, piratez maps can go up to height = 30... which is roughly linearly (8-times) slower
2/ vanilla maps have visibility limit = 20, piratez has limit = 40... which is much worse than linearly slower... I don't have exact numbers, but it can bring any CPU to its knees
3/ also tons of new features in OXCE+ (e.g. indicators, night vision, LOS checks, etc.) are slowing down rendering quite significantly... again I don't have exact numbers, but I would say it's about 50-100% slower in worst cases
All in all a tall map in piratez can easily render and animate 50x slower than a normal vanilla map.
PS: also, if you have FPS counter enabled, don't believe what you see... even if the game barely manages 5 fps, it will still show a lot more