The days of the 21-61 and all the arsenal Saiga conversions is probably over until the Russian sanctions are over. That said the 104/107/Sam7 Bulgarian guns are available and nice rifles.
When you talk about Century, you have to be careful...there are foreign arsenal built guns, like the WASR 10 and the N-Pap/O-Pap series, there are kit built guns like the M70, GP1975, etc., there are Gen 1 US C39 guns, and there are the new C39v2 guns and the new US stamped guns. All have different characteristics. Guns built in Romania and Yugoslavia come in neutered and get converted back to normal. This used to be subcontract, and now, I've seen them doing it in house, which is good...they've got some new guys over the past few years from GD who have re-vamped the manufacturing operation into something impressive. Still, on these guns, you get what the foreign arsenal gives you, and although everything is test fired...they crank them out for export over there at the cyclic rate. The Yugos are smoother and more refined, as long as no chrome in the barrel is not a show stopper for you. The Romanian guns can be made to run and are the proper weight/handling characteristics for an AKM, but I think of them as assembled parts kits. Most likely need to have some edges smoothed out. The kit build guns, built on US receivers and barrels depend on who actually built them up and the quality of the parts to begin with. YMMV. The new V2 C39 models have been very impressive, and making a milled receiver that takes the more available stamped furniture is a big plus. We've shot a few of these guns, and I've been very happy with the performance. The stamped guns look good, also, but I don't have any trigger time on them yet. These may be winners. The guys from GD know manufacturing, tolerances, and QA/QC and I've been very impressed in our dealings.
I also have a few Interarms guns that are quite nice. They are essentially kit builds, but they use chrome lined US made barrels that shoot very well, good receivers, and they are built on a proper build table. They've got a guy or two from Arsenal of Bulgaria working there, so it's guys who know how to build rifles.
I haven't shot the new Palmetto Guns, so I'll reserve comment, but that's another option to look at.
I've heard very good and some, but far less not so good reports about WaffenWorks 74 builds, but once again, I have not handled or fired these, so I'll not comment.