There are a few differences in the APIM’s themselves over the years. In 2018, the daughter board was replaced with a significantly improved version, along with some other updates for chips, etc., throughout the rest of the APIM itself. Here is a image of the Gen 1/2 (2016-17) daughter board…
and the Gen 3/4 version (2018-2020).
Recently in the 3.4.21194 update, a qualifier was added to the AL2HMI Bridge, which required 90% of QML files to be updated. (about 2900+) This was done to speed up the display performance mostly, with a few other improvements. Taking into account that the older hardware of the Gen 1/2 units, this would have some affect on performance, but not like it would on the Gen3/4 APIM’s utilizing the hardware the changes were designed for. But at the end of the day, the ‘laggy’ Gen 1/2 units are just old and outdated. Replacing the daughter board on the older Gen 1/2 units with the Gen 3/4 board will yield much better results, the performance will not be on par with the Gen 3/4 units. This is not a straight forward replacement however, and the payoff in respect to cost and time is really not worth the effort.
The best value is a straight replacement APIM, either ‘J’ or ‘K’ series (also labelled as ‘3’ or ‘4’, which some people mistakenly associate with Gen 3 or 4). These designations are the part number (model) year designators. ‘J’ or ‘3’ = 2018, ‘K’ or ‘4’ = 2019, etc. Don’t bother with the 2020 units as they may or may not have incompatible screen drivers, etc., depending on the vehicle they came from. Those are the ‘L’ or ‘5’ units.
If you old screen is in good shape you can reuse it on the newer units.
You can find info on many APIM models here… Hardware Database - CyanLabs