I thought I'd provide an update as to how my 'journey' is going!
Win10 1909 Multi Session on Standard_D4_v3
Imported from Marketplace, 'Optimise Windows Image' not selected as if I select this it's impossible to get the UK Language settings sorted! Import reg keys to meet the Horizon requirements (Kill the store, windows updates etc)
MDT to install: latest FSLogix, Office, Chrome, Teams (system wide installer with reg key for multi-session), Adobe Reader, OneDrive
Custom Start Menu xml to resolve lots of broken stuff (Note that pinning items to the Taskbar appears to be no longer supported in 1909)
Run Once Script (configured on Farm): Had to write a batch file to rid myself of the en-US language pack (suspect that something in the VMware unattend.xml is adding it)
We're using FSLogix with a new profile and configured to delete at logoff so we expect initial logon to be slower, with subsequent logins much faster. Login in time are calculated on the time from double clicking the Pool / Farm through to seeing the desktop.
Initial login around 45 - 50 seconds, some of this is sub optimal Group Policy, 10 seconds of it is a lovely 'black screen'!
Subsequent logins around 15 - 20 seconds, a couple of seconds of this is the lovely 'black screen'!
When I get some time I'll be looking into this further...
Currently investigating how valid this is for Windows 10 Multi Session, the doc from MS doesn't mention Multi Session but TheVDIGuys does.
Need to look into what settings from the OSOT can be implemented. If I Optimise using OSOT it breaks searching on the Start Menu.
I'll try to provide updates on my journey, hopefully this will accelerate the journey for others :-)