A basic ETRS system with 120 back, wl finder, body, 75mm standard lens and caps, etc. can be had for about $200 in the Toronto area. I see a number of them on CL from time to time. Add a hand held meter and you are up and running. The rest of the system is fluff and will not yield better results or make you a better photographer but, helps in making the photograph. Start with the standard lens and one that covers what you normally shoot, either wide angle or tele and learn the 2 lenses.
I have the 50 and 40mm lenses with my system and of not think I've used the 50 in decades but do keep the 40 on it most of the time. I'm not into the "normal" focal length in any format so the 75 that is quite good also gather dust and I tend to use the 105 macro as a 2nd lens. The 250mm only gets used on a tripod. The key to the system is to decide what you actually need and what s a nice to have accessory. When I bought mine back in the old days, I pretty much emptied the bin and today realize that I do not use 90% of what I bought. 3 extension tubes that I've used maybe a half dozen times, a lens doubler maybe the same amount, the motor drive that makes the camera a true elephant weight and other items. I'm not sorry I bought the stuff. Lenses 40, 50 75, 105, 250 and the doubler makes 80, 10, 210, 500. So, I cover 40, 50, 75, 80, 100, 150, 210, 250, 500. The doubler does not degrade the results significantly at least to 8x10. There is also a fisheye and several zoom plus a shift lens and a 500mm so as for lenses, the sky is the limit.
Admittedly, I do not have to choose between 6x4.5, 6x6 or 35mm as the ETRS has a 35mm back so the system also is my 35mm system and I have a 6x6 camera. The 6x6 is a Rolleiflex and is lighter to carry than the Bronica. But, it is not as versitile. It does have a large number of accessories but at a cost. The TLR you mention, is more versitile in that it has the ability to substitute lenses and is a bellows based camera menaing it can focus closer. But it is not light. I've thought about getting the C330 a number of times but each time I try 1 out, it feels too unwieldy and out of balance with the 135mm lens. The Rollei feels better. You may want to look for a Yashica Mat-124G of its earlier stable mates that are the most successful Rolleiflex clones down to using the same lens accessory flange for things like lens hoods, filters, and the Rollei can use the Yashica accessory telephoto and wide angle lens sets. The Yashica lenses are very good. I used one until I got my Rolleiflex and still miss it.