@Niara: We apparently posted simultaneously, so I'll add on to my previous post to address your new OneD&D points.
Bards I'm not necessarily opposed to Bards having a restricted spell list or spellcasting. Imo 5e bards were too good at spellcasting at too bad at combat for their "jack of all trades" role. Illusion and Enchantment specifically seem to be an ideal focus for bards. I agree with you that the specifics might be a bit too punishing/restricting.
Memoized-by-level restriction See my post above; I don't hate it. Unrestricted memorization in 5e gave casters a significant power boost. I suggest that casters can prepare lower-level spells in higher level slots.
Exhaustion Can you explain why "one point of save DC is worth about two points of attack bonus"? It is because ST spells are (roughly twice as) more powerful than weapon or spell attacks, so an enemy making their save is ~twice as bad? - Buffers will be more likely to fail their concentration STs, and concentration makes it so they can only really concentrate on a single spell at a time. Idk, "buffer" as a role doesn't really seem like something you can focus on in 5e...not unless you include debuffing enemies, which at that point requires STs. - see my previous post on a potential Speed penalty.
Flying + Restrained Huh, I didn't notice that. I hope they'll give the Hover trait to everything with a magical, non-physical fly speed...
Grappled I like grappled as an opportunity attack. Tanks can actually hold space. - I dislike the change to make it against AC. We lost flat-footed and touch AC, now we've also converted contested athletics checks into hit-against-AC. :\ - You can attempt to escape a grapple by making a Shove attempt against enemy AC, as an attack-equivalent action, and then move away. Overall, it's an interesting change but I agree it needs work.
Help I like that you have to be proficient in the skill in order to help. Someone without Arcana proficiency shouldn't really be able to help a Wizard recall some magic lore. - Your example about wasting their Help action won't come up often imo. Especially with the grapple vs AC changes, very few (unknown beforehand) skill checks will take place during combat that you'd actually spend your action to help on. Helping Attack Rolls still works the same after all.
Hide...depends. I like the simplicity of a DC 15 check, but it is a bit weird. - In your example, all Bahamut and Tiamat have to do is move until they can physically see you, and then you're automatically found. No perception check required. Whereas if you're invisible or hidden behind a wall at a distance greater than their move, it makes sense they'd have to spend an action to actually locate you by e.g., your footsteps. This also makes the (relatively common) Legendary Action: Search more useful.
Move Action They did the opposite of what I would want. I'd prefer if you had to move your entire movement before or after attacking, but could swap movement types freely. - E.g., a ranged character moving 15 feet, stopping, drawing their bow, aiming, firing accurately, then moving 15 more feet seems like it should require a feat or fighting style: "shot on the run." - You should use up proportional movement for each type. E.g., base speed of 30 ft and swimming speed of 20 feet. If you move 15 feet on land, that's half your movement. Thus, you can now swim 20/2=10 feet OR run 15 more ft. - Action Jump is dumb
Resting A 10-hour long rest can be split into one 8-hour chunk and one 2-hour chunk. If the 8 hour chunk (the first 8 hours, the last 8 hours, or 8 hours in the middle) satisfies the resting requirements, then you've successfully rested for 8 hours and spent 2 hours of your Adventuring Day...sitting around. I'll agree that it could be worded better.