Designing my first CoreXY printer, would appreciate some opinions. (2 replies)

Currently using a Taz 6 that I'm relatively happy with, but a little bit jealous of you guys' fast and nimble coreXY machines.

Always wanted to build a printer from scratch, initially figured I should just do budget build of an already proven design to first understand each designs limitations and progress along. Considered D-bot, HyperCube Evolatution, and Voron1.5/2 (made a post in Reddit but only got limited responses) but ultimately none of them offered exactly what I want in a printer. So I decided to just go ahead and get a drawing going to figure everything out as I go

This is what I have so far:

• 9mm rail on X carriage, 12mm on Y and Z
• 3030 frame, 2020 X carriage and maybe print bed frame
• 300x300mm 3/8" thick Mic6, 110v silicone heater
• Print head removable with two forward facing M4 thumbscrews, interchange between Bowden and direct drive
• AB stepper motors in the rear to reduce front clutter, idler bearings next to the motors for tensioning
• Front top bar placed towards the middle of the frame for more forward accessibility
• Haven't design the joints yet, they will be printed in ABS for quick revisions, possibly mill out aluminum replacements once I nail everything down

These are my goals:

• 300 x 300 x 300mm
• Rigid frame and scale-able to larger sizes
• Interchangeable print heads - love this feature on my Taz 6
• Z=0 using nozzle contact - makes using different length nozzle/print heads easy.
• Fully enclosed (including wiring loom/Bowen tube) with active heater
• Would prefer to avoid auto bed leveling
• Good visibility to the print area and easy access to print head.

Would be great to achieve but could wait till future revision:

• More elegant 3 point leveling with thermal expansion compliance
• Nozzle wipe pad before homing - limited by travel range and footprint
• Magnetic bed with quick swap spring steel + PEI
• Easier belt tension system

Below are a few question I would like to get some feedback on before I progress any further:

• Please double check my belt path, my understanding is that there are certain section of the belt that needs to be kept parallel with direct of axis, do you see any problems with my tension method?.
• Corner brackets for 3030, between Misumi and hidden, what is your preference?
• Still unsure how to drive Z, for some reason I'm feeling a little iffy about lead screws. Not sure how much I can trust the straightness of them, where to get quality screws? My Taz6 has thick screws and are constrained both top and bottom, I know this design is usually frowned upon, but it works well. How about belt drive? how much reduction would I need to lift/hold my 12" x 12" x 3/8" Mic6 plate?
• GT2 belts, is real Gates worth the extra price over those from Aliexpress? Should I use steel core or larger size for driving Z?
• Regarding silicone bed heater, how much advantage is using a heating that is exact to the bed size vs one that is 3/4 (or 1/2) the size? Aluminum is a good heat conductor but if using an undersized heater does heat distribution becomes an issue on printing?
• Was initially planning to use a Ramps 1.4 (that I'm familiar with) and run 24v + TMC2100, but all research suggest I should just get a DuetWifi which is new to me, anything to look out for? (ex. I need special steppers for 256 microstepping?)
• Building an bed frame, an extrusion box seems the most obvious but are there more elegant bed solutions for 3 point leveling?
• What are you guys opinion on PEI thickness, I've installed a ~1.8mm thick PEI on my Taz6, it's basically indestructible and prints pop off easy, but it did developed very minor "ripples" after a year worth of ABS heat cycles, but I'm unsure if it was caused by it's glass bed's uneven heat distribution.
• Exturder, specifically when in Bowden mode, I've built many true and trusted Wade's and also done a few revisions myself, any other extruders I should consider? Direct drive, only choice will probably be a Titan for size/weight.

That's all I can think of for now. any feedback will be appreciated it! Thanks!