You can create any sized tilesets for TileD. It is only recommended to not go over 1024x1024 when using TileD for your sheets if you are going to embed the Tilesets for your game -- because your game will start chugging if you're using bigger Tilesets effectively causing slower load times.
But if you wanna just use it for mapping and specifically parallax mapping... by all means and make sheets that are HUGE.... like disgustingly huge.... -- while keeping your maps small since, those images will be the ones going to be loaded.
The other way to handle Autotiles is to rebuild them to be TileD compatible.
https://forums.rpgmakerweb.com/inde...rallax-mapping-made-easier.97739/#post-888643
You will convert your Autotiles this way and effectively have to map using 24x24 grids. BUT in Archiea's manual, (I believe she also recommendings tiling using 24x24 for a lot more flexibility. With corners and 'thinner' than usual corners.
I also don't recommend (imho) using the autotile converter if you are already using 24x24 grid sizes mainly because in my use of it... It gets really confusing which corners or 'variations' each are without a lot of experience -- aside from that if you're mapping using 24x24 grids all that can be already achieved with a little more 'time' (more tiles to manually draw). But it's up to you, to consider amount of manual input vs amount of mental effort to learn the pattern of the generated auto tile using the plugin.
Again, if manual stuff isn't your thing, check out the tutorial via the link and just convert your autotiles like that. It makes mapping a lot faster for the most part, but due to how autotiles work in TileD -- it really does have its own quirks. Nothing that can't be remedied by a little more effort.
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and to the point of using more than 10 sheets -- for most maps that's not really a problem, and to Dark's point, making unique tilesheets per area is an option -- but from using Time Fantasy (and heavily modifying Jason's assets -- you get a whole ton of variations) and with a lot modified assets rather than doing individual sheets per location (and because in excel, I approximately came up with like 100 areas (equavilant to 500+ maps) I didn't want to create sheets for 100 areas -- so in my circumstance I ended up making modular sheets per object type...
As an example, its because if I wanted to make a village with 5 different types of roofs or 2 or 3 different types of exterior walls... etc... I would effectively use up 7-8 out of 10 sheets. (before TileD would start acting up)
And so... in my case, I actually just use TileD to make Parallax Maps because it's a lot more user friendly than Photoshop -- its also more efficient with some of its features... Other than that, once I've exported my maps, and they still need some additional tweaking... I just tweak the exported image via Photoshop, loading up my modular sheets once again.
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But that's just how ended up working with TileD. It really depends on the amount of assets you're going to be piling in. With Basic MV assets (bought or RTP), I really don't think staying under 10 is an issue. Even using just the given TF assets, I don't think staying under 10 is an issue -- but I went out of my to modify Jason's assets to the point that I couldn't figure out any other comprehendable way organize all the assets I was to produce, just by recoloring variations and reiterating them from every/any situation I could think possible...
I hope something in this wall of text helps you get a better idea of your options.

Good luck problem solving!