So I am aiming to have a near vanilla experience for my first Oblivion playthrough.

I am am a little unwilling to use a lot of mod managers/script extenders and such programmes right now.
I am thinking of going with the Unofficial patches and Darnified UI for now.
Will there be any problem if I install the patches without mod managers? Darnified UI apparently can be installed thorugh extraction and a bit of tweaking files.

Is there any other mod which is necessary for first playthrough which is easy to install?
Is the enemy levelling thing really annoying? What is the easiest way to deal with that problem?

Thank you in advance.
:)

If you want to stay vanilla, one option is to use a cheat to change your level if the scaling becomes a problem. This way, you can make it so that the enemies will stay at a lower level (though be aware that this only affects enemies that haven't spawned; you might need to leave an area for 73 hours to get the existing enemies to be replaced with their weaker counterparts). Note that this will also affect the random loot you find, which is *also* scaled by level, as well as things as the strength of the souls that you can find to trap, so there are trade-offs involved.