I am returning my 2nd mini. The first one’s Y axis didn’t move at all and this one skips line infills as well as a few other issues. These printers were my first 3D printers and now I am considering If I should get the TAZ 5 and maybe upgrade using the topics with the rail extrusions and all that? What would you suggest for a first time user? Should I get my 3rd MINI and hope for the best or go with TAZ 5 this time?

Depends. How much do you like bed leveling on the mini? The 5 doesn’t have that out of the box. The larger build area is nice too. Is go with a taz over a mini, but that’s just me.

I actually don’t like it. I want to it myself. I can also make that system later as I learn. I have seen someone already do it. I also want to upgrade to aluminum extrusion rails. How much of a prior experience I should get to upgrade my future system to yours? Can I do it as soon as I receive it following your procedure or you suggest me gaining experience first?

I would suggest getting to know the printer for a week or two first. That way you will know if you have any quirks you will want to resolve before altering the base configuration.