Each year, Corey Pronman of the Athletic does an organizational review of all the NHL teams farm system. It is mainly focused on 22 and under talent within the organization. Last year, the Penguins were 28th. This year, they've fallen to 30th, with only the Capitals behind them.
https://theathletic.com/2003157/2020/08/24/2020-nhl-organizational-rankings-no-30-pittsburgh-penguins/
Poulin is the only one graded at "very good NHL talent." His main weakness is his footspeed, with some scouts questioning now that he has filled out, if what you see today in terms of skating/footwork is as good as its going to get. Even then, Pronman says he has skills to be solid NHL player.
Legare came in 2nd, followed by POJ, Hallander, and O'Connor in the "Legit NHL player category." Like Poulin, his main concern is his skating, but Pronman says he has seen an improvement in this area from his draft year. It's still not a strength, but has a smoother stride.
On POJ, his biggest negative was offensive ability. He's not a PP QB type of guy, but he is excellent defensively.
On Hallander, average footspeed and slightly above average puck skills. His strengths though, are high hockey IQ and compete level.
On O'Connor, good hands and good skating stride.
Pronman listed Puustinen, Cam Lee, Will Reilly, Bjorkqvist, Caulfield, and Maniscalco as NHL potential. His blurb on Maniscalco:
Josh Maniscalco, D, Arizona State-NCAA: Maniscalco was a top player for a strong ASU team, playing all situations. He’s a very intelligent and competitive defenseman with size. His game lacks much in terms of speed or skill, though.
Pronman also had a reply in the comments section to someone, stating, if the Penguins are keeping pick #15, you are hoping you get a prospect that is as good orbetter than Poulin.
People also asked for opinions on Bellerive and Almeida, and his response was pretty much the same for both....he liked what both players did in Juniors, but "skating for their size" is a concern. I'm guessing that means as smaller guys, skating should be above average at worst, and neither are really blowing anyone away with their skating ability.