Some time back wsa2_32 made a WC with Trebizond finishing in something like 1654. You can find it in the AAR forum. I think he did paint the whole map. As far as I know this is the fastest one we have some documentation of. There was one post I read 1,5 years ago or so where one person claimed he had made a WC as France around 1610. He did not give any details. Pity vStein did not finish his WC Turbo attempt with Orléans. He could have set a WC record in speed (although he did not aim at a true WC).
But today I don't think it is possible to paint the whole map in your color. Not with the new colonising rules.
He also made a WC with a pagan nation, Benin. That is also an accomplishment.
I made a WC with one of the candidates for the worst possible 1-province minor in Europe, Albania. But that was in 1.05 when you could make TA with everyone and compensate your low income from tax and production. I don't think I could repeat it today.
Just to start the bidding I can give you some stats from my last GC, a WC as the Mughals. That was 25.417 VP. Easily breakable, I did not strive to maximise my VP but anyhow, as I said a starting point. My monthly income at Dec 1 1819 in that game was 4.741d at stab 2, 1607 Tax, 1109 prod, 1772 trade and 258 gold.
Biggest COT value was 1766d in Delhi (my capital). That is an interesting kind of record I think.
Largest tax income of one province was also Delhi 26,4d.
Largest production income will probably be taken by a christian owning Zacatecas and having converted it and with the capital in America (I believe the penalty for not having the capital on the same continent also decreases production value but I am not sure).
Largest supportable army/navy will be taken by someone who has the patience to build shipyards and CCs all over Eurasia-Africa.
In one game I built 100 Fine Arts Academies (the last ones were incredibly expensive

), believing my stab cost would be zero but it turned out there was a cap. I could not enjoy more than the 50 first or so.
One fun category would the number of dead soldiers. Or perhaps the opposite, least number of army units lost during a WC GC. In my Mughal game my losses were infantry 7.890.000, cavalry 2.090.000 and artillery 6.260. roughly 50% in battle and 50% in attrition.
Largest production and trade effiency would be taken by someone with patience enough to build manufactories all over.
There you have some new categories!