I was doing a session today with lots of people trying out Tagtool. I was using an A1474 5th Gen iPad Air with OS 12.3.1 several people mentioned that when they drew or wrote their name the line did not keep up with their finger, so I watched and they were correct, it was a tiny lag but noticeable, many of then were quick with the scribbling and Tagtool just could not keep up, the writing skipped. Also, while they drew the Menu, Network, Fullscreen, Rewind, Animate & Panels would dim, the Aim, Erase, Zoom & Select stayed lit (is this suppose to happen?). Once they released their finger the dimmed words would light up again. As a note, I had one .png in a layer and about six layers of very basic drawings. (I did a test to see if the old Tagtool on my 10.3.3 iPads could keep up with the finger on fast scribbling and it did, amazingly). Is the A1474 5th Gen too slow to run the new Tagtool? Do I need to go out and get a new iPad to get New Tagtool to run like the old Tagtool? Let me know your thoughts on this. None of this ever bothers me, so I did not take note of it until the people pointed it out, I draw very slowly 
Also, will it ever be possible for the old Tagtool on older iPads to join sessions with the new Tagtool or should they just stay in their own world? Thanks, Cliff
This weekend, I upgraded to an iPad 6th Generation (Best Buy in US sale $249.00 less $65.00 trade in on the iPad Air A1474) and The New Tagtool is running nice and smooth keeping up with fast scribbling! Because we have been doing a lot of group Tagtool sessions I now have several MD510LL/A iPad 4th generations with 10.3.3 installed that runs the old Tagtool like a charm, New Tagtool works “OK” if you don’t mind some lag. Therefore, if I have too many guests, I put up another projector/router/AppleTV set up and use Old Tagtool for the Newbies, the paint area is larger and there is no lag making the experience more enjoyable. I noticed that the Old Tagtool is no longer showing up at the app store, does that mean if I buy some refurbed 4th generations will I only be able to download the New Tagtool?
Since iOS 11 Apple has officially withdrawn its support for 32 bit apps. So the “old” Tagtool does not show up on the Appstore anymore. It should be possible to re-download it via the “purchased-section” in the store, but it only works on devices running iOS 10 or below.
The “new” Tagtool is a 64 bit app and a complete rewrite of the code. Older iPads really suffer from this technological shift. We only use our Air 1 and 2 models during workshops, because they can´t handle a decent performance anymore. Also stopped updating the iOS because it is slowing down the devices even more.
An iPad Pro from 2015 (and later) are the best models so far for artistic multiplayer sessions.
Best,
Mat
Thanks for all the great info Mat, much appreciated!