OK, so Burrow's OL was worse than Tua's. Watching him play it is obvious how quickly he processed information. Burrow had a higher Yards Per Attempt, and while 6.7 vs. 6.3 doesn't sound like much, it is significant. Burrow's Average Yards Per Game were 268.8 vs. Tua's 181.4, which clearly shows that Tua was throwing less and/or shorter throws. It's a lot easier to throw when your defense produces takeaways and keeps opponents from scoring too much. When you're always playing catchup the pass rushers can pin their ears back and attack. Watching Burrow play you see he instantly reads defenses and processes information at a ridiculously fast rate. That may come with Tua, but he doesn't have it at Burrow's level yet.
So batted passes, that has nothing to do with vision downfield, and where Tua really did not shine was in his checkdown preference, so he threw fewer intermediate throws. It may be because he's not fully healed form his hip injury, but the fact remains, he didn't make those throws. Against Buffalo when he was forced to chase the game it was not pretty. By the way, Justin Herbert had 7 of 595 attempts batted down, whereas Tua had 2 of 290 attempts batted down, so even in that metric we need to be clear that 2 vs. 7 is misleading. So passes batted down shows up in both completion percentage (Herbert 66.6%, Tua 64.1%) and INT percentage (both tied at 1.7%), so if you're giving an advantage here, it would be a slight advantage to Herbert. But that's not the real issues with size. Taller QB's see the field better and tend to do better at downfield throws--which is where Herbert outplayed Tua--while the smaller QB's need to see between the OL more than the taller QB's do. The muscle is more of a metric of durability, and I'd say that both Tua and Herbert passed the rookie durability test as rookies, whereas Joe Burrow was injured and that was a major problem for the Bengals.
No, sorry, the statistics show that Tua was the least accurate of the three rookies. Tua's completion % was 64.1%, which was lower than Burrow's 65.3% and Herbert's 66.6% so while Tua may prove to be more accurate, as a rookie, he was the least accurate of the three. I am confident that Tua will prove to be an accurate QB. That is not an area where I really worry about Tua's game--particularly with the short passes.
So there are two primary types of QB's in the NFL, the old model is the big pocket passer who can take a hit, and I'd say guys like Big Ben and Phillip Rivers are examples of that type. The newer and more modern type of QB is more mobile and with that comes sacrificing some size, and I'd say guys like Kyler Murray, Lamar Jackson and Russell Wilson are examples of that type. A great example of that type would have been RGIII, but one lower body injury and he was never the same QB. Tua is not the elite runner those guys are, and he's not a big tough guy either. I do worry about his durability though. He didn't challenge the middle of the field on intermediate throws because of his low velocity, but maybe he's just not seeing it as well yet. Sometimes it takes a while for young QB's to adjust to the speed of the NFL and the complexity of defenses and playbooks. I suspect when he has a proper offseason (not a Covid-wierd one) and a fully healed hip, his velocity will return and his confidence and processing speed will improve significantly. But based on year one ... he's definitely behind the other guys, despite having by far the better defense and when he was having a bad game he was pulled. He will not have that luxury next year, so let's all hope he makes those improvements.