2. Alot of it kind of does preclude the idea that Venamis is Bane's superior. On implication/hype, he's the most powerful and masterful sith lord in galactic history up till his time, which would put him above the likes of Exar Kun, Marka Ragnos, Naga Sadow, and even Emperor Vitiate. And Sidious straight up said that Bane and 4 others were his most powerful predecessors, not most renown. Point being that Bane, as the Sith'ari, is implied to be a being of both immense power and renown. If Venamis fits any of these bills, feel free to address why.
The underlined part is what you need to pay attention to. Venamis didn't exist at that point.
The publisher's summary says Malgus, Bane, Talzin, Plagueis and Sorzus are Sidious' 5 most powerful predecessors.
On the other hand, pretty much every other source in Star Wars, which aren't created by the publisher, concludes that each successive Sith in Bane's line became more powerful and knowledgeable in the Dark Side than their master. Other explicit sources conclude that Vitiate is better than Malgus and Sorzus. So while the five of them are clearly among Sidious' most powerful predecessors, they aren't a strict top 5, thus you can't exclude Venamis by principle.
Ergo, none of it applies to Venamis. This, however?
The Sith had changed. The Sith had grown, had adapted, had invested a thousand years' intensive study into every aspect of not only the Force but Jedi lore itself, in preparation for exactly this day. The Sith had remade themselves.They had become new.
-Revenge of the Sith
I find that to be quite compelling given that Venamis was trained extensively at the end of this thousand year line by none other than one of Bane's most powerful and experienced successors. Trained so extensively that he could shield his Dark Side alignment from Plagueis himself, and sufficiently that Tenebrous awarded him the Darth title (the title in of itself means shit, but it suggests Tenebrous took no half-measures in training him).
“I knew I could draw you out, Darth Plagueis,” the Bith said.Plagueis dropped all pretence and faced him squarely. “You’re well trained. I sensed the Force in you, but not the dark side.”
“I’ve Darth Tenebrous to thank for it.”
“He made you in his image. You’re a product of Bith science.”
The Bith laughed harshly. “You’re an old fool. He found and trained me.”
Plagueis recalled the warning Tenebrous had nearly given voice to before he died. “He took you as an apprentice?”
"I am Darth Venamis."
-Darth Plagueis
So from what we know, Venamis was indeed pretty badass. Though it's clear he doesn't fully benefit from the RoT scaling, and interestingly enough Plagueis speculates that Venamis would have done well in Bane's era. Also what's important to note is that Tenebrous and Plagueis were at odds in regards to the Sith's future for decades, and at that time they were both looking for Force sensitive acolytes to help them, which is presumably around the time Tenebrous found and began training Venamis.
Blood analysis had revealed a high midi-chlorian count, which to Plagueis was further indication that a being could have great potential in the Force and yet still be inept [ngl I find this funny since it implies Plagueis finds Bane inept as a Sith].
[...]
An investigation of the ship had yielded data that might have surprised even Darth Tenebrous, who had provided the ship. It seemed that well before he had confronted Plagueis or learned of his Master’s fate, Venamis himself had been scouting for potential apprentices. Plagueis could not help being impressed, though begrudgingly. The young Bith would have done well in Bane’s era. Now, however, he was an anachronism, and by extension, Tenebrous also. That Tenebrous had targeted him came as no shock to Plagueis. He and the Bith had reached an impasse decades earlier regarding execution of the Sith imperative.
[...]
He had assumed that, given time, he would have been able to win Tenebrous over, but his former Master had obviously pronounced him unfit to don the mantle of Sith successor, and had looked elsewhere. The unbridled desires of sentients were a blessing to the Sith, for those desires birthed an abundance of zealous and audacious beings who could be used to further the cause. Plagueis had been instructed to be on the lookout for suitable beings, just as Tenebrous had been when he had discovered Venamis.
-Darth Plagueis
I think based on what we have, Venamis is at least as strong as Bane, possibly stronger, and he didn't reach his full potential.