I'm way beyond the anal nonsense about different geometries, tracing arcs and so on, as any differences tend to be academic and totally inaudible once the hobbyist attitude slowly becomes music listening as the years pass.
The Techie arm is/was designed to put the inner null point on a protractor at 57mm or so from disc centre (my mid 70's Dual 701 tonearm is exactly the same). The effective length is fixed as is the offset angle, so no need to worry about all that as the greatest theoretical error will always be at the opening grooves where it's inaudible and academic due to the faster 'read speed' at the beginning of side.
The difference on my tonearms between Stevenson and Baerwald (forgive spelling if not correct) is one to two millimetres maximum in the headshell slots, the Stevenson 65mm or so alignment bringing the cartridge forwards more in the headshell slots from memory. I'm damned if I could ever hear a difference back then when I thought it mattered and I certainly wouldn't and cannot now
Just set the blasted pickup up the way Technics tell you to, make sure VTA is as accurate as you and maybe a pal's eyes can tell you, set downforce (which should be within 10% accuracy)
and play some bloody records on it The vinyl medium is so flawed and basically distorted (albeit in charming-to-the-ears-ways) despite being able to entertain our human ears so well, it's no point getting truly anal about it, really it isn't. Technics knew what they're doing when designing their tonearm geometry and no way would they get this all wrong over the last fifty five years or whatever!
As for inner groove distortions, this can be in the pressing, especially if played by a groove-grinder in the past as some of my earliest LP's were. Later cuts were a bit on the 'hot' side in terms of level and with some pickup-phono stage matches, the latter can overload with nasty results. I love AT's cartridges which have a lower output than traditional (3mV rather than 5mV at 5cm/sec) and these tend to be safer with less expensive phono stages. I'd add that tip quality can make a *huge* subjective difference at high frequencies, a bonded elliptical not always as 'clean' as a naked elliptical stone, an ML having pin-sharp definition (maybe a little too much in some models) and the later Shibata tips a lovely (to me) compromise of refinement, unforced detail and low surface noise.
Just don't EVER expect vinyl to be always as consistently 'clean' in tone as digital most often is.
