As many of us do, I like to use a number of mods that alter Winterhold & the college as well. Because they are both in the Tamriel worldspace, rather than their own area - this can cause a lot of objects to be rendered at once. This of course leads to poor performance.

Personally, I like having as high a framerate as possible, and the college has always been a place that my frames suffered (especially in the courtyard). So, short of making the college it's own worldspace with a load door, this is the best solution I was able to come up with.

So how does it work?

This mod adds windows to all of the open arches in the courtyard area of the college, as well as filling in the gaps in the gate. When you are INSIDE the courtyard, it toggles on a number of large occlusion boxes outside the college walls, which hide the vast majority of Winterhold and the surrounding mountain objects. If you are on top of the college "walls," it does nothing and you will have the nice view (and -50 FPS) that you are used to. If you or an NPC opens the gate, it will toggle off that box specifically so you don't see any weirdness. It will then re-enable it once the gate has shut.

This mod also adds auto-opening and auto-closing of the main gate. This is to ensure that the occlusion box that is behind the gate can be on most of the time. It will auto-open & close as you approach, and also auto-close after it has been manually opened after a few seconds.

I'm pretty sure I got all the edge cases where the player would be outside of the college and the boxes would be enabled. That said, even if they did stay on somehow, you would need only to pass into the courtyard triggerbox to resolve the issue (this really should never happen though).

How much FPS will you gain?

That depends. There is also a potential that you will lose FPS or stay around the same (occlusion has overhead itself). It is very dependent on your hardware & what mods are in your load order. I would guess that most people will at least get 5-10 FPS when looking in the direction of Winterhold, but you will have to try it and see for yourself. If you gain none, then simply remove it! If you look at my screenshots you can see a few comparisons and what relevant mods I was using when testing.

If you're wondering why I don't have the occlusion boxes also on when you're outside the college (e.g. looking at the CoW from Winterhold), it's because of how the engine calculates what you can see. Essentially, the occlusion boxes must be quite large in order to block the entire view of the player if they were, say, backed up against the door to the Hall of Elements looking at Winterhold. If I had those same ones enabled when you were in Winterhold, assumedly hoping to gain performance by having non-visible college objects occluded, it would cause all kinds of visual issues. It would be possible to make a different set of smaller ones that were on when you were outside the college instead, but in my testing there was no notable performance increase from doing this. Though, there are likely some setups where you would achieve an increase. I hope that made sense.

Scripts!! NOOOO!!

No need to worry. The scripts are very quick and only activate based on trigger boxes & the gate. They will fire when you enter and leave the courtyard, someone opens or closes the main gate, or on loading the cell. These are all fire & forget and do not run continually.

Requirements

Base version requires nothing. The versions made for specific college overhauls... require those overhauls.
All versions are an ESL-Flagged ESP.

Compatibility/Load Order

General
Should be compatible with anything that does not edit the main gate. I have overridden the vanilla gate script (MGGateTriggerScript) to make sure the occlusion toggling works properly, so that needs to override anything else including it. The window & gate meshes are separate and do not modify any of the base game meshes so they are completely compatible.

College Overhauls
Versions of the mod have been made for:

• Vanilla/Magical College/Juniper's College/JK's College/Any other overhaul that doesn't touch the gate or it's trigger box
• Immersive College of Winterhold
• Obscure's College of Winterhold
• Ultimate College of Winterhold
  

You only need 1 main file, just download whichever version is correct for your load order.

For those of you using various college combo patches: 

• To put this simply, if you are using a combo patch that uses either ICoW, OCW, or Ultimate (e.g JK's + OCW), you want to use those patches instead of the vanilla. This is assuming that you still have ICoW, OCW, or Ultimate enabled in your load order. I can't promise these will work, but there is a high likelihood they will operate without any issues.
• If you're using a combo patch that merges 2 of the vanilla ones, for example JKs + Magical or something, the Vanilla patch will still work fine (probably).
  

I also "fixed" the vanilla gate mesh using the wrong shader to enable the glowmap. If you don't like this, there is an optional file that will return it to the more vanilla look!

Not Compatible

• This mod checks if you have completed "MG01" - The first college quest that unlocks the main gate. If you are using a mod that circumvents it, the gate occlusion will not work properly. It's not game-breaking but it may have some unexpected behaviors.
• Don't use "Governable Gatekeeper" from Misc. College of Winterhold Tweaks. It will interfere with my gate & my mod adds similar behavior already.
  

Known Issues

• If you are using Alternate Start - Live Another Life, and choose to start as a new member of the college, the front gate will be open and the occlusion box also enabled. Simply close the gate once and this issue will be resolved.
  

LOAD THIS MOD AFTER ANYTHING THAT MODIFIES THE COLLEGE