Is Heyman’s current run bigger than ECW?

No. ECW literally changed the game, and essentially everything you see in wrestling today was influence in one way or another by ECW.

From the edgy reality based storylines that lead to the attitude Era, the lucha libre style coming to America, "hardcore" style wrestling with blood and weapons.....

WWF/WWE and WCW were able to adapt, thrive, and evolve based on the talent and aspects of ECW that they stole and were able to showcase to their television audience.

If it wasn't for ECW.....WWF would have stayed where the wrestlers were cartoon characters and occupations, and WCW would have stayed with that Southern Wrasslin' style.....but the 90's were a different time, and ECW led the way and Paul saw the writing on the wall and he saw what was hot and trendy or what was soon to BECOME hot and trendy, and Paul sort of took those risks first, and then Vince and Eric swooped in and got all the glory.

Fair points, but one could argue ECW derived from Mid-South Wrestling (the bloody, hardcore style actually started in the southern US, and Heyman discovered that as a tape-trader), FMW, and Joel Goodhart's Tri-State Wrestling Alliance. And the original owner of ECW wasn’t even Heyman.
So one could argue an equivalent to ECW still finds a different way to exist without Heyman, because the roots already existed without him. But I don’t think his current 2012-2023 run has any way to exist without him.
And one could argue that if you’re comparing accomplishments within someone’s career, the part that couldn’t exist without said person has to be considered bigger than the part that might have still existed without them.
Just throwing out theories. I love ECW too, and maybe no equivalent could have existed without him. But it’s possible.

Not really he is basically a background character not a main character (or booker/promoter/etc)

Never understood how someone with so much wealth and connections could look like a regular cars salesman though

Overall, no.

Is current his best on screen work? Absolutely

Well, yes. He’s in the very top tier in wrestling. ECW was a glorified developmental league. Much like Elimination Chamber being bigger than all of Sami Zayn’s bingo hall matches combined, the bloodline storyline and Brock Lesnar ending Undertaker’s streak are bigger than all of Heyman’s bingo hall shows combined.

That said, he has also managed scrubs like Curtis Axel, Ryback and Cessro in this run.

Yeah. Running an influential developmental league or indie show is cool and all, but it’s just not on the same level as Roman Reigns and Brock Lesnar.

Triple H signing Johnny Gargano and making him NXT champion is a thing that happened, but it’s not as big a deal as Triple H’s feud with Daniel Bryan, let alone Triple H’s feud with The Rock.

I think time will tell. as it stands, ecw has had a bigger impact. but the Roman/Heyman story is arguably the biggest one of the generation for many wrestling fans, so who knows how big it’s influence in time will be.