so if I understand corectly DBseo have the xame functionalities as VBSEO?
DBSEO does not contain all the functionality of vBSEO; we've opted not to implement certain features that are either not directly related to SEO (Likes), are outdated (Linkbacks / Pingbacks are no longer relevant for SEO, social sharing has replaced it) or detract from performance for little gains (Acronym Expansion, Relevant Replacements).
I would suggest that you examine the current vBSEO feature set, determine what features you use, then check to see that they are found in the list on this page:
DragonByte SEO
We just need to import our confuguration XML and we're good: page titles, meta descriptions, links ..every critical part works flawlessly?
It's impossible to guarantee it works flawlessly, vBSEO is certainly not flawless
That being said, as you can see by our News forum, DBSEO currently receives weekly change & bugfix updates

We are determined to fix all bugs as they are being reported.
One thing I should note: URL structures are sometimes slightly different from vBSEO to DBSEO. If you are using forum titles with no forum IDs in them, stopwords are not filtered from those URLs as they are in vBSEO. This is to correct a bug report we received where stopwords caused certain forums to not resolve correctly, and caused multiple forums to have the same rewritten URL causing confusion.
My vBulletin is 3.8x and I am upgrading to 4.2.2, what will be the procedure to install BBSeo so that it functions exactly like VBSEO?
Install DBSEO -> Disable vBSEO -> Perform the htaccess changes as per the readme.txt file -> Use the vBSEO importer in the DBSEO AdminCP.
Note that the vBSEO importer is a Pro-only feature.