I have a williams FP-CZ rear peep sight on my cz 455 trainer. Fits snugly on 11mm dovetails. It works very well and is an improvement over the already great tangent sights. The aperture it comes with is a bit large for my liking so I bought an aperture with a smaller hole (0.05 inch) and a larger diameter (0.5 inch). However, I coudlnt find either in Canada and had to buy them from the US. It works fine with the stock front sight of a cz 455, but the width of the front post can obscure smaller targets at longer distances.
The front globe sight situation is a bit more tricky. AFAIK there is no globe front sight mount or adapter for the CZ455. The BRNO mod 4 adapter does not work. One option to consider would be to remove the front ramp and replace it with a Williams 3/8 shorty dovetail mount (or equivalent). Then mount a Lyman 17 (or anything with a 3/8 dovetail) 3/8 front globe sight. Problem is the stock front ramp is sweated or glued on so removing it is a PITA and probably involves going to a gunsmith.
A front globe sight is doable, but I think you would be better off buying a rifle that already comes with globe sights. The savage mk II FVT is honestly great value for money (never tried this specific MKII variant myself, but I have shot other MKIIs and they shoot great). Alternatively plenty of good but pricer options on the EE like the BRNO 4.