Can low PCs connect to servers with no issues?

So I’ve just got an i9 9900k with 32 GB of ram. If I were to run a modded server, could my family connect to it with lower end PCs with little to no lag or issues?

Is there anything I can do to make them able to join issue free, obviously other than get them better computers?

How and what affects lag and FPS drops? I’ve read that’s the main issue with Minecraft. Can we use it with optifine? Should optfine be installed on server?

Minecraft 1.14 – villagers won’t pick up food

I’ve tried everything I can think of. I’ve moved the villagers 200 blocks away from anything like beds or work stations, I’ve given them beds and work stations and taken beds and work stations away and everything in between.

No matter what I do they just refuse to pick up any food. I’m spawning them in in different spots just to test things and the only way I can get it to work is in a different world.