Royal Mail OBA anyone have one? Looking for advice

My post office has been taken over and the new staff are clueless so someone here may be of help.

I have a new OBA with Royal Mail. (online business account)
so now I can use ppi and Royal Mail 24 and 48 but not sure on the steps RM have set out.

So these are my questions..

I create labels for my 6x4 printer and print let’s say 5 rm 24 and 5 rm 48 all small parcel, I bag them in separate bags all 24 in one sack and all 48 in another.

add the tags to the bags and write on order number and location number but print a manifest
i then take the bags and manifest to the P.O. and they accept it and I leave it all with them and that’s it?

I realise each service and size has to be in separate bags but do they all go onto the same manifest?

i haven’t actually started using it yet as I’m waiting for my sacks and tags but trying to get an answer out of rm is a nightmare.

as far as I can remember yes it all goes on 1 manifest, log into OBA and just add each service with quanity size and avg weight, comfirm order then print, but don't fully count on my info as it was rare I used OBA to send the mail cos we use Linnworks sotware which created the manifest for me :) but when Linnworks was down I had to do it via RM OBA website manualy :( :( which was a ball ache