Great video, I have a ton to say.
I def agree with your tier rankings. I would move a few runners around, however.
THE FAVORITE FOR GOLD
T. Cheruiyot - Defending World Champ can win any kind of race. Fast opener? Yeah, he can go out 55 flat solo. Fast finish? Yeah, he can run away from a field. Ran 3:28.41 Monaco '18, also dropped a 1:43.11 PR at altitude in Nairobi before World Champs last year. With peak fitness, can't see him losing to anyone (except maybe a certain E. Manangoi)
GOLD OR BUST BABY (NO MEDAL RUNNING HERE)
J. Ingebrigtsen - Youngster from Norway isn't just keeping up with the big boys anymore - he's one of them now. The world's #2 1500m man with a 3:30.16 PR demonstrated impressive consistency over the season with many sub 3:32 / top 4 races, coming up just short in Doha. Would he have done better if he hadn't run the 5000m? We'll see in Tokyo...
E. Manangoi - The former 400m man turned middle-distance star has been injured over the last year or so. On form, however, he has never been beaten by his teammate Cheruiyot, including an early season win in '19. It will be interesting to see if Manangoi can reclaim his spot as the number #1 1500m man in the world (and in the Rongai camp).
He's just TOO GOOD for me to place any lower.
LET'S GET SOME HARDWARE LADS
R. Musagala - Last year's breakout performer, but his rise has been otw for a few years now after medalling behind the Rongai men at the African Championships. In '19, was very consistent on the circuit, running 3:30.58 twice and notching a few more sub 3:32. With big meet exp from his Doha flameout, expect to see a better showing in Tokyo.
F. Ingebrigtsen - The middle I-bro has been slightly overshadowed by Jakob, but his progression remains strong into his mid-late 20s. Filip was not as consistent last year, and ran 3:30.82 and 3:31 low. He has big meet exp; won bronze behind the Rongai men at the 2017 World Champs. Maybe Jakob's success will light a fire under Filip next year.
A. Souleiman - Wow, how long has this guy been elite? Only a year older than Filip or Elijah, the Soulman ran 3:30.31 in 2012, aged just nineteen. Since then, he has hovered around the 3:30 barrier, impressively consistent but never truly breaking through as the world's best. Notably, he also has a strong 1:42.97 PR. Something to keep in mind - he bombed out of the heats of the last two WCs, after a 4th place in Rio.
LET'S GET SOME HARDWARE, BEFORE WE CAN'T ANYMORE
T. Makhloufi - Hey, is it a big meet year? Then expect to see this guy pop up! Makhloufi, king of disappearing during the regular season, did the same act again last year in Doha and was successful, walking away with the silver medal. The Makh-Daddy has incredible 800 wheels (Rio Silver, 1:42.61), but was born in April '88. Like the OP stated, Tokyo delay will hurt as time is not on his side... but then again, the 3:28 man has shown he can peak better than anyone. Maybe we'll see another 1:44 800m during practice...
M. Lewandoski - This guy did the textbook move-up in events ( a gazillion years of 1:43, many close podium misses), and was immediately rewarded. Ran a smart race, grabbed a fatty 3:31.46 PR and the bronze medal in Doha. What more could you ask for? Well... again, the Tokyo delay isn't the best for him, but maybe these old guys need to save their legs anyway. I could see yet another tactical final in which Lewandoski somehow sneaks a medal, but who knows?
M. Centrowitz - Wow, feels mad weird to put Centro here. Age wise, he does go with the Algerian and the Pole; everyone else above was born in the 1990s. I will never doubt this dude - I think he is easily one of the best tactical runners of all time, and deserves a TON more credit for medalling at the 2011 and 2013 WCs as a youngin. We all know the glory of that Rio race; the question is, can he do it again in Tokyo? I think joining BTC and getting stronk (13:00 flat 5000m PR) is good considering the current tactics presented by the field. Cheruiyot can and will run away from a field; no more silly Asbel Kiprop shenanigans. Centro already has medals - he's not going to run from the back conservatively either. Doha was a preview of future Centro: balls to the wall, imma go out hard. That day, he didn't stick on them quite like he wanted to (from the interview), but if he fully commits to a fast race in Tokyo, Centro has the talent and experience to make some magic happen!