The server will have good days and bad days as far as lag goes, it all depends who is on and what bases are loaded. Expanding the render distance would add a considerable amount of lag. It would likely cause anyone with less then a diamond pick to quit within the first few minutes of playing on the server. Its a delicate balance between the amount of players, render distance and lag. If you change one you affect all the others. Setting the render distance higher might be better for players with big mob farms, however, in the long run it will produce a lot more lag and cause players the go elsewhere.

With each year a new cpu comes out that's better than the one before, however, with each release mojang adds more features that require more power. I remember back in 1.8 when I could get 88 players with little to no lag and render distance set to 10. Then mojang added enhanced mob collision that caused mobs to calculate collisions with all other mobs, creating an exponential amount of lag (<num of mobs>^2, 2 mobs = 4 collisions, 100 mobs = 10,000)

I would love to be able to run a full server at render distance 15, but with current technology and vanilla performance, it's just not possible. 1.13 is suppose to focus on performance, but it's likely they will also add more features causing the net performance gain to be minimal.

- Crafty