Couple of things. For the EX3400 LED situation, I believe this was covered under PR1329903. This should be fixed in 18.1R2 and above. This is the situation where when a cable is removed LED stays on.
I would suggest at this time, the best option for EX3400 and/or EX2300 is to go to 18.2R3-S1. You will likely need to follow KB 31201 - https://kb.juniper.net/InfoCenter/index?page=content&id=KB31201&actp=METADATA
Now once you are on this code, you should be able to upgrade, without needing the extra steps - SW will take care of clean and file space automatically via PR1417441 change.
As for other PR mentioned in this thread, PR1428703, that is fixed (right now) only in 19.1R2 and 19.2R2, and I believe PR1417441 is also resolved there, BUT neither of these is out yet.
I do not have any personal experience with 19.x on these platforms.
Just FYI JTAC recommended is generic recommendation for majority of customers, and does not target any specific PR or feature functionality.
I will look to see if PR1428703 can be expedited to be in 18.2R3-S2, which will likely become next JTAC recommended.