First please don't not mix several unrelated questions in one topic in the future. It really gets inconvenient mixing all these. Thanks.
> cacheManager - OK, I am nitpicky. I like having this
Not required. Please see: https://www.zenphoto.org/news/caching/
> class-video - Need for video content
Not required, unless you want to use video and audio files.
> comment_form - need for comments
Not required, unless you want to use commentts.
> deprecated-functions - Do i need this
Not require as it's comment says if you are using official stuff.
> mobileTheme - for mobile to have different theme
Not required and outdate technology. For granted official thems are not responsive which is the way to go. But there are good 3rd party /half official themes for that.
> multiple_layouts - OK, I see purpose
Not required and the theme require special support.
> PHPMailer - for email
Not required as zenphoto
> rss - Do i need this
Not required unless you want to provide RSS feed for your visitos to subscribe to naturally (which you should if the site is public)
> security-logger - OK, I see purpose
Not required but useful.
> site_upgrade - OK, I see purpose
> slideshow2 - adds slideshow if theme does not have, correct?
No, a theme requires support for it. See the theming tutorial.
> uploader_http - Do i need this
You need one of the uploader handler plugins enabled if you want to upload.
> userAddressFields - Do i need this
Not required at all.
> zenpage- what these does this support?
https://www.zenphoto.org/news/zenpage-a-cms-plugin-for-zenphoto/
Second
> I ran into a strange issue.. I created an album, copied in about 40 photos. this is part of a gallery with 1600 images already. As soon as I copied in the photos... Pow... ZP was hung up. Slow. Non responsive. albums not showing up. in admin. Delete the photos and all goes back to normal.
Image processing is a memory and power consuming server task. Please see: https://www.zenphoto.org/news/problems-with-albums-and-images/
> Does ZP start processing pictures as soon as they are added? Should I have just waitned? if it isprocessing the photos, what is it doing?
https://www.zenphoto.org/news/caching/
> I removed xmpMetadatamedia and openstreetmap, and all went back to normal. images don't cause things to hang up.
I cannot say if there is a relation but might as they naturally access image album data. But not necessarily.