The big thing: Support has significantly reduced gold and are much weaker early. The biggest gold difference I managed to get was like 3K but that was me being super oppressive and getting a lot of tower plating gold. On average, whether behind or ahead, the difference is probably like 300 gold. I've had games where I get completely demolished in lane and then somehow be behind like 500 gold. I've stomped lane and only been ahead like 400 gold. It doesn't really feel much of a difference. Plus I've been buying a lot less pink wards because you have so little gold to work with. It's not really a bad thing personally but I think it makes pink wards a lot more valuable and I would only recommend buying if you know you're going to contest an objective.
I am conflicted on the support item. The charges charge faster but you have to decide if you want to use it to hit champions (you get more gold for this) or use it for the execute (which doesn't give you minion gold for the kills but can help with wave management). There's also like no early stats on the item so you're incredibly dependent on the champion's base stats. It only gives you like 30 HP, and 25% health and mana regen. So you're gonna do a lot less damage because you don't get AD or AP on your first item anymore. I do like how the item transforms into different items but you're probably only gonna get 2-3 items in like 30 mins.
I think engage supports are gonna be a lot harder to play. You really have to punish mispositioned people. If the enemy team plays super safely and you just use the charges on the support item to execute minions, you get a lot less gold now. I think they buffed the HP on the engage supports but the tank items are expensive. you can say what you want about mythics but the tank mythics gave armor and MR. Locket is the only cheap item that gives armor and MR, so it's probably going to be the first item for a lot of tanks because all other tank items are either armor or MR only. Add to the fact you get a lot less gold, Tank/engage supports just feel weaker in my opinion, especially if the enemy team's AP damage dealer gets fed.
Enchanters are gonna thrive, but only if you're using the charges on poking enemies. They have so much tools and item to choose from. You can also get a mini crown of the shattered queen if you want. But they have so many opinions to choose from item wise.
I haven't played a mage support yet but I think they suffer from lack of gold as well. If you're playing a mage support, you probably have to take a lot of kills if you want to stay relevant since the role has less gold overall.