Is character customisation different between Smash Ultimate and Smash Wii U / 3DS?

I've watched a bit of Super Smash Bros Ultimate gameplay and wanted to ask a bit about the game. I feel one of the most important parts of the Wii U and 3DS versions was the ability to challenge people using the customizations that you worked hard to get the equipment and specials for. I want to find out if the customization feature is any different from the 3DS and Wii U games, and check there is no way that it has been downgraded.

I've seen that the game offers a mode called World of Light, in which you can gain spirits that give you stats and abilities. Can these spirits be used in multiplayer?

The game seems to be amiibo compatible, but I don't know if their functionality is the same or not. Are amiibo that are setup for the previous two Smash games compatible and is their functionality any different?

Thanks for any help.

Mii Fighters can be created directly in Smash Ultimate, which is handy since you can't create them on the Switch menu. Mii outfits are still collectable in Switch.

All custom moves have been removed with the exception of Mii Fighters which have the same custom moves as in Smash 4. Their custom moves are edited in the settings used to create Mii Fighters.

Spirits can be used in local multiplayer matches and the World of Light. They can add a larger variety of buffs, stats modifications, and even nerfs. They function somewhat similarly to stickers in Brawl but with a larger range of effects and they can be removed from a character without drawback (removing a sticker causes you to lose the sticker).

In addition to spirits is Dojo training. There are various Dojos obtained through playing the World of Light which each providing a range of stat modifications that can be applied to spirits, for example increased jump and weight but decreased speed and attack. One Dojo (Slowpoke) can remove other Dojo stat modifications.

Amiibos function similarly to Smash 4. Any amiibo for any of the playable characters, including those for Smash 4 and those not created for Smash, work in Smash Ultimate: a list of these amiibos is here. Certain amibos also grant you a spirit that corresponds to the amiibo, also contained in that list. Contrary to the rumours, amiibos don't unlock characters instantly.