My main harnesses/bags are Wildcat* with some Alpkit and some Revelate. I’ve also a couple of Apidura feed bags but don’t use them much.
The only bag that will be bike specific is a full frame bag, come companies do generic full frame bags but it’s a bit of a lottery as to whether they are a good fit for your bike. A partial frame bag holds almost as much and if you choose the right one you should be able to fit a water bottle in the frame as well.
Saddle bags will depend on whether you want to use them with a dropper or not. Don’t get one that’s too big as it will only encourage you to put lots of stuff in it which can lead to severe movement. 8-10L is more than enough.
Handlebar harness/bag – try and find one that doesn’t foul your cables. A harness lets you use different size dry bags depending on how much kit you’ve got. It also means that if you wear out a dry bag you don’t have to replace the harness as well.
Stem Cells – just about anyone will do – not a lot between them in my experience but the Apidura are quite a bit smaller if you are worried about knee strike.
There’s a few reviews on Bearbones including the Lomo – https://bearbonesbikepacking.blogspot.com/?view=magazine
*Wildcat did cease trading earlier this year but they’ve started up again and from their website it looks as if production will start in a month or so.