I'm not someone who speedruns myself, but I do watch quite a lot of Pokemon speedrunning, primarily the side games, with Mystery Dungeon being my favorite. Recently Wh0misDS pushed for a new WR on English Wii U Blue Rescue Team (2:20:33, a record of almost 4 minutes over his old one for Wii U) and has been going for japanese runs as a result.
One of the big things with Blue Rescue Team are missions, which you want to get "near missions" (missions that want you to find an item in a dungeon, which can be completed without having to do anything if you just happen to have the item already), there's also the dungeon Uproar Forest, which is entirely mandatory despite potentially seeming optional to start with, where you will also need to get two exclusive items to the dungeon (Chestnuts) to progress. It is possible but unlikely to find 2 in a single run, but you will always find one on 9f, and if you have a pokemon with Pickup recruited they will always pick up a Chestnut on 9f if at all possible. Partner choice is something, the run uses Cyndaquil due to it having a better midgame, but Squirtle is often used for a better early game with Skitty not needing the better partner for the midgame if you get a TM in the shop to link with tackle
There's a lot more that goes into this but i think i'll stop there, the run was uploaded on youtube about 3 weeks ago, it's pretty cool, you can go check it out if you're interested
One of the big things with Blue Rescue Team are missions, which you want to get "near missions" (missions that want you to find an item in a dungeon, which can be completed without having to do anything if you just happen to have the item already), there's also the dungeon Uproar Forest, which is entirely mandatory despite potentially seeming optional to start with, where you will also need to get two exclusive items to the dungeon (Chestnuts) to progress. It is possible but unlikely to find 2 in a single run, but you will always find one on 9f, and if you have a pokemon with Pickup recruited they will always pick up a Chestnut on 9f if at all possible. Partner choice is something, the run uses Cyndaquil due to it having a better midgame, but Squirtle is often used for a better early game with Skitty not needing the better partner for the midgame if you get a TM in the shop to link with tackle
There's a lot more that goes into this but i think i'll stop there, the run was uploaded on youtube about 3 weeks ago, it's pretty cool, you can go check it out if you're interested