Anselmp

There have been lots of posts like this. Read the answers to others and follow the general advice.

I use Anna's Hjerim to bypass this quest.

It would help others if you said which mod caused the problem.

This makes no sense. What exactly have you loaded?

Not enough information. Having reached that point it seems unlikely that your modlist will help much, assuming that you have checked that all of your mods are correct for SE - the latest versions are now mostly for AE, although many are the same for both. If your internet connection is WiFi you will get occasional blips. Also check your memory - dramatic changes from one area to another can stretch it a bit if you have left other things running.

I believe the Engine Fixes mod reverses the switch that turns achievements off.

Whenever I make major changes to Skyrim the SKSE usually stops working for a time. (The move to AE and changing from C: to E: were the two most recent). Since you have been following the general advice you need to look at some of the detail. (Incidentally, I am older than you). Not having Steam up causes SKSE not to be recognised. Running Skyrim once will set Steam up, but too late for SKSE, so coming out and starting again may do the trick. You must of course still use the SKSE loader, not the Steam one. Do you have the Engine Fixes? You really should have these. Part 1 is loaded by Vortex in the normal way, but you must load Part 2 manually. You could benefit by reading the posts for this and Skyui, since they contain useful information beyond those specific mods.

Most of the more recent mods are flagged as incompatible with the latest version of PoE2. My version of the game was downloaded more recently than the date of many of these. Does anyone know what the problem is?

Try Penitus Oculatus

Look at 'Dragon Age Origins - DAO Followers ...' which adds Anders and Isabela from DA2.

If you don't use followers, that should be fine. I've been packing my game with Anna's NPCs, Interesting NPCs, Citizens of Tamriel and some individual NPCs, which I swap around and put in my various houses. But then I'm the sort of person who reads poetry and novels and so on. There are quests that require one to leave followers at home or simply work better that way (eg Maelstrom). I've lost interest in the fighting for now, so I let the followers do it or use a one hit kill weapon.

As you help so many others you deserve a reply of some sort. Combat animations are more likely to be ok if you limit your followers, particularly mages, not just to avoid crashes but to be able to see what is happening. Also, if it is not very precise there may be more difficulty in avoiding hitting melee followers who jump in front. Personally, I would avoid such mods.

Riften is a dump. You have the option of adopting children. Unfortunately even with mods the limit is six. What would help would be the ability of your stewards in your houses also to be able to adopt so that they could all have a couple of children playing around. I never have room for more than 2 from the orphanage as I don't like to leave the others begging on the streets. There is a mod that provides a large orphanage/boarding school in the middle of Whiterun which is quite a good start but needs cheering up a bit.

No. I've been there countless times with no problem. So you would have to look at the ones that could affect that environment that I have not used : Northern Grass, Enhanced Landscapes, More Bandit Camps, Immersive Encounters look the most likely. As for SoS - use at your own risk. Which followers are with you? If only vanilla, say how many instead. You seem very fond of mihael.

This list shows SkyRe still in use. If any of your mods have been updated check whether the patches are still required. You have too many patches for comfort. You have lots of overlapping environment mods. Just because some work happily together does not mean a whole group of them will. I doubt if all of those mods have been properly ported to SE. Do you really have to have all of the towns and cities changed? Use Easy Lockpicking.