I will be away for a few days so any further reply from me will have to wait until after the weekend.
Regarding OTA (Optical Tube Assembly) and other acronyms, I know this can be a bloody nuisance. You are reading an article and come across one and then have to sift back through it to see the first time it was used!
Anyway concerning your question. Bresser is a distinct and different manufacturer from the people (Synta company) who make ‘Skywatcher’ and ‘Celestron’. (Bresser may be Taiwanese, but I am not sure – You could google it.) The problem comes in that brackets and fittings are probably not interchangable. You see for the 150mm Celestron, I attached a ‘Skywatcher’ mounting bar (plus rings), to mount the 80mm guide/finder. Parts are identical.
The Chinese moderately priced stuff is quite good.
Now for my SCT’s I was at first worried about the 30% plus obstruction by the secondary. Theoretically it does drop some contrast. In a practical sense for the F10 or F11 units, you would notice very little (if any difference), from a refractor. Of course out of focus images are a donut. Also, your SCT would be 127mm, 150mm or even (I would recommend) 200mm, which still weights in at around 5kg just like a 120mm refractor. At the loss of a small amount of image quality you have extra lightgrasp and resolution and more convenience in use – and no spurious colour.
Still the refractors, being traditional, have allure, and the big ones in my early days were very expensive – so I wanted one. (The dreaded ‘I wannas’.) I have one and it is nice but….