Tonearm relative to Plinth alignment

I'm not sure I follow you - are you thinking that loosening the 3 screws may allow the arm to rotate back to its parallel position? Another option may be the VTA set screw. I'm not familiar with the Basic, but my Ittok has a single set screw on the collar - and when you loosen it you can adjust the vertical alignment and also rotate the arm.

I'll defer to Doug's view on the effect, but I still think you can straighten it by rotating the arm in its pivot. If you look at this picture, you can see one set screw that fits horizontally into the pivot plate (ie the round plate that fastens to the plinth). If you loosen it with a hex key you the arm will become free so you can adjust the vertical alignment as well as the alignment to the plinth. Finally - forgive me for stating the obvious - be very careful of your stylus is you loosen this set screw. You may want to prop up the arm with something so the vertical position can't drop.

This is how Linn arms adjust VTA. If it were me, I'd straigten it, though I would not redrill the mounting holes.

on the basic plus tonearm, there is a slot on the cylinder that only allow you to adjust the height, but one can not rotate it, so alignment to plinth can not be adjusted

now I see . . . this is different than the Linn Ittok, and Audioquest PT6 I previously owned. With those it's very easy to create this alignment issue(which I have done when not paying attention). As noted, it's aesthetics, not function, so if there isn't an easy solution then leave it alone.