In my experience, the high points of the Beogram ranges are the likes of the 4000/4002/8000/8002, with the latter two models in particular being capable of superb sound when loaded up with an MMC20CL or MMC1. The Thorens/Acoustical Beogram 3000 models from the 1960s are also no slouch, sonically.
As to the later models, I'm afraid I've always been underwhelmed by the performance of the TX2/5005/5500 etc. type linear trackers. Their internal construction is neat but greatly economised compared to the earlier models and you can hear it in their sound. For this era of equipment, I much prefer the radial tracking Beogram RX2/2000/5000 etc. models, which is excellent news as they command much lower prices!
That said, even some of the more lowly models can be a surprise. I remember buying a mint Beogram 2200 purely to acquire the equally mint MMC20CL that someone had fitted to it. I fitted an MMC20S to it before selling it and remember being greatly surprised at just how good the 2200/MMC20S combo sounded!
As to how they compare to modern turntables, this is all down to personal taste. Personally I'd take a Beogram 8002/MMC1 over a comparably priced Linn LP12 and a Beogram 2000/MMC4 over a Rega Planar 3 but many would not...