Wanhao I3-Replacing plastic parts with metal, and questions about a Bearing Block mod

I have been wanting to replace what plastic parts I could with metal ones for my Wanhao i3, and was surprised to find quite a few options exist already, although I had some questions about a few of them.

The first one that caught my eye (and the main one I cared about) was the CNC-milled metal extruder from Micro Swiss:
https://www.amazon.com/gp/product/B06WVB6CYD/

Pretty much exactly what I wanted (I was originally planning to see how possible it would be to use lost PLA casting to produce such a thing myself before I saw these), although I was confused why it seems to include a pre-drilled hole so one could add PTFE tubing for the flexible filament mod, instead of just using the design that raises the upper guide on the extruder plate to narrow the gap instead. Is using PTFE tubing instead of just reducing the size of the gap itself superior somehow?

I also noticed that an all-metal hotend and an improved carriage plate were normally purchased with these as well:

https://www.amazon.com/dp/B01E1HANLS/

https://www.amazon.com/dp/B01MUAMRN7/

I remember reading before about an all-metal hotend being highly preferred, but I admit I am at a loss about what exactly it would be replacing. I don't notice any non-metal parts on my hotend other than thermal tape that came wrapped around it. Also, while reading up on it, I saw several issues people had (namely with PLA) about this metal hotend causing jamming. Can anyone help clear this one up for me?

As for that third one, the carriage plate, all I could find out is that it's more rigid and thus helps with bed leveling and preventing the bed from becoming un-level from bending/warping. Is that all it does, or does it help keep movement on the Y axis smoother too? I already have a glass plate on my bed, would I need to bother this this if it's only for keeping the bed straight if I already put glass on it?

Also, while unrelated to the other three, I also found this:
https://www.amazon.com/dp/B071SD7B4Z/

A Z-axis bearing mod was also something I was planning, but I couldn't decide on a material. I was previously considering PETG over PLA for rigidity, but was told that it's just as flexible as PLA, PLA would also not be ideal, and ABS would be tricky to print. The only real issue I have with that one is that as others mentioned, it's kind of on the pricy side, but metal certainly seems ideal over plastic for the purposes of bracing an axis, especially since this will take up much less room than the plastic versions as well.

So, has anyone used any of those above four metal mods for their Wanhao i3? Do they have any advice on if I should use them or stay away?

As for the bearing block mod:
https://3dprinterwiki.info/di3-mods/bearing-block-mod/

Most of the versions of this mod I see replace the three bearing blocks with two instead, and I was curious as to why. Is having two actually superior to having three? Does having three actually cause more issues than having two would?

And another reason I am asking is because I was looking for replacement bearing blocks (From what I understand, the one the Wanhao i3 uses are SCS8UU type?) and most of them come in packs of four. Would using four be better or worse than using three (I was wondering if the reason for this would be because three were an uneven and asymmetrical design)? Or would using two still be better than either three or four of them? Another problem is trying to find a decent supplier of them, since many of the ones I found had some reviews of people complaining that there was at least one if not more that both appeared different and had defects included in the set.

Right now, the main ones I am focusing on are the metal extruder and the bearing block mods, I do also want to apply the metal Z-Axis brace although it's somewhat expensive, and so far I don't understand what the point of the metal hotend or replacement carriage plate are.

The non metal part of your hotend is a ptfe liner inside the heatbreak. You wont see it from outside. At higher temps this tube can melt and jam your extruder. If you are only printing in pla this is a non issue. As far as the 2 bearings vs. 3 for the x carriage from where I stand it looks like this mod is either trying to reduce drag on the x axis OR it is trying to get a few more mm of travel on the x axis. But here's the thing. There are a plethora of modifications out there for every printer ever made. And none of these mods actually came from the manufacturer of the printer. They are all stuff you or I or some other fool came up with in their own imperfect mind. It is up to you to look at the mod offered and discern if it is going to help or hurt your printers performance. If you do not know if a mod is going to help or hurt you then you probably shouldn't be doing it. And if you are performing a mod based solely on a problem you read about, then when it is done and your printer does worse than before you started that will be your bad. Modifying these machines is SUPPOSED to be for chasing better performance. You are supposed to identify specific issues with your printer first and then find a mod to address that specific issue. Haphazardly applying mods to your machine that you aren't even sure what they do is likely not going to end well. I will tell you now converting to all metal parts is going to make for a noisy machine that might shake it's own screws loose. Metal screwed to plastic can last long be quiet and not vibrate so much while drawing out the infill.