Personal contention: Bowser beats Toon Link.
https://m.youtube.com/watch?v=pDafKGkyd1w
Yeah no I'm really not seeing it. (Granted this isn't 1.1.3, but I believe this accurately showcases Bowser's woes in the neutral. I'd post more videos but I'm pressed for time.)
The existence of the Uthrow followups matters so much in this MU now.
How? I know Bowser's new grab follow-ups heavily increase his damage-racking capabilities, but this comes with the cost of having an incredibly linear gameplan on account of having piss-poor out-of-shield options. Also, Browser's dash > grab is still frame 14, making it rather telegraphed; it's susceptible to down-thrown bomb > Bair cross-ups.
Edit: apologies, I must be blind - the dashgrab is 10.
Bowser runs faster than Toon Link,
By 0.06.
and such can make his way through the projectiles in a regular fashion by frequent powershielding. The projectiles are one hit wonders, so Bowser only needs to keep a rhythmic powershielding going and continue to pressure.
I feel like we're discussing Link and not Toon Link here, because Toon Link plays keep-away and Link plays a more grounded come-at-me game; it's important to distinguish the two. Toon Link players are skilled at using projectile traps like the return on the boomerang and up-thrown bombs to keep their opponents in shield while they cross-up. Powershielding across the stage, while practical, isn't a free win, and I feel as if you're overstating it a tad.
It also sounds like you think Tink has no CQC against Bowser when his frame 6 jab beats out just about everything Bowser has. Dashgrab also has a FAF of 48, meaning spot dodge > Utilt can land heavy damage on Bowser and put him into disadvantage with Uair as the finisher.
Bomb and Rang pulls take commitment, commitment that Bowser can use to swoop in and grab or dash grab and get Uthrows going,
For this to actually work, Bowser would need to be right up in front of Tink when he pulls the bomb or boomerang. No smart Tink is going to do that at close range.
or simply jump in and Fair Tink out of; even if the Tink can get that projectile out, that Fair will be a very worthy trade.
See the above. Most Tinks use retreating jump > bomb pull, and they shouldn't do that at close range. It's smarter to read the incoming grab and pivot boomerang.
Tink can get the damage up no problem, but when it comes to getting the KO confirm, the game becomes a very tense version of chicken, and one that Tink just can't afford to lose. Tink's projectiles lead into moves that hit primarily to the sides, so Tink can't really force vertical juggling opportunities until Bowser dies unless the Bowser is just really stupid.
Bomb > Uair. This will also put Bowser in his favorite position on stage: airborn, where he's susceptible to getting pelted by Tink's projectiles and Uair airdodge frame traps.
Speaking of disadvantage, Tink's projectiles also eat Bowser alive offstage.
He's got a tether grab, so if he misses, he's getting grabbed, so that's out.
Conditioning. Bowser will be repeatedly conditioned to shield because it's the only way he can approach through the wall of projectiles. This is also a good option before Bthrow kill percent because U-throw puts Bowser in disadvantage.
Tink has to land at some point from item tossing, so if Bowser managed to powershield or dodge through that one time, that landing just got a hell of a lot more harder now with the presence of Bowser's pivot grab. And if he didn't get through the projectile and got followup'd on, again, Tink's hitting from the sides, and Bowser is quite the persistent bugger in staying alive horizontally. Max rage Bowser Uair kills Tink as early as 70% or so, and you can bet Bowser will be regularly hitting those percentages.
Platforms don't seem to exist in your hypothetical scenarios. If this were on FD, sure, this may be a problem, but even Smashville supplies Tink with ways to escape Browser's linear approach options (and a means to punish his approach if he tries to chase with downthrown bomb).
I don't see how Bowser gets 70% so easily in this matchup. The bottom line is, he suffers in the neutral, his options are limited to power shielding making him susceptible to grabs, and Tink arguably has comparable reward with his grab considering how bad Browser's disadvantage is. He also destroys Bowser in both disadvantage and edgeguarding.
runs circles around him in the neutral, as do 
