Hi Jarno, nice to read you again and thanks, as always, for your help.
 

This is here, so it's said; "you insane". As in, you are modifying a game, and you want to use a pre-existing character... WTF ! Just start a new one, and if you need, cheat to get the stats you want, and throw the saves away.

You're right, I didn't check if there were still a functioning version of ShadowKeeper for the EEs so that I could avoid the import.
 

You need the BG1EE and the SoD DLC for it, now there's several ways to get it, and but the best way is to not purchase the BeamDog version, as they come separate, which is not conducive to EET's install in a single game.
And as to the fact, that the DLC comes as a .zip file, you need to install the DLC Merger tool on top of BG1EE+SoD, so the .zip file is intergrated, before you use the EET install onto the BG2EE to bring the data to the BG2EE to intergrate it into EET.
Don't let the name fool you, it's a pentalogy, not a trilogy. As in, it has the content of BG1, BG TotSC, BG SoD, BG2SoA and BG2ToB. Yes, that's 5.

I'm feeling a little bit overwhelmed   but I'm still motivated   
1) I bought the Steam version of all the EEs and SoD seems to be one with BG1 EE -> So this step seems to be ok for me.
2) DLC Merger tool, never heard of it before, I'll look into it to better understand what to do.
 

And why did you choose Longer Road ? Here's the latest community maintained. Just download the .zip file.

Because with ascension was one of my favorite mods back in the days, I'd love to be able to play it again.
 

Don't overlook the EE games game options, there are several that are badly hidden in various amounts of Graphical User Interface blocks that have bad designs. Features such as zoomed in menues accessable by use of tiny menues. As in, use a 3840x2160 resolution 28" monitor, and find the menues that were intended for what, 640x480 by default, in a tiny center portion of the screen that you might not even be able to read the text from, so you can't tell that there's option for zoomed in menues.

This also daunt me a little, right now I've a 32" 4k display, this might be a big problem.

PS: For what I'm reading in other posts of the SHS community there are equally enthusiastic comments about Beamdog as also very critical one about the results of the work done.
I'm starting to have some doubts.

Anyhow, trying to recap what I think I've understood from your precious tips, the correct steps for my endeavour are install in this order:

1 BG1 EE
2 Separate zip DLC SoD
3 Install DLC Merger tool 
4 BG2 EE
5 EET
6 Ascension
7 Longer road

Hi all (hoping this is the right place to post it),
i’m an "old" gamer who played several times the original BG games.
I’ve also played enthusiastically, several years ago, BGT-WeiDU, i was always too much eager about the number of mods I wanted to play in my installation, this greediness of mine unfortunately caused bad playing experience and didn’t allowed me to finish Trilogy without blocking issues, stuttering, extreme slowness, etc.
After 7 years discovering the EEs modding possibility made my heart warm again and, obviously, full of memories, so I decided, for the sake of old times, to buy them all (also Icewind Dale and the masterpiece Planescape: Torment) to try another time the Trilogy playthrough.
So now i wish to start a new game and go through all the three BGs trying to do only simple things:

- Import my old character from my early 2000s games

So I'm writing here, asking for your help, hoping to understand If I am missing something important about my goal and the mods chosen.
Are there some tips I should know or am I missing out mods I should install that improve stability or are some must have (although I don’t want too many fearing it may “ruin” the game)?
Or in general is there something I should know or do to improve stability of the trilogy game?
Thanks for your help!