Is there a way I can turn off specific races or class options in my campaigns yet? Or do I have to just hammer it into my players heads that in my world certain races don't exist.
Do what I do, write a one page detailing your game. Highlight the choices that are verboten for world reasons such as Warforged, Half-Elves or the like. You should also do this for all rules you have decided not to include such as Multiclassing and Feats.
This is something that should always be discussed at session 0. Also, good and courteous players should and will clear any character plans with you, the DM, before introducing the concept to the rest of the group. Worst case scenario, you just have to say "No" in front of everyone. Don't play it as a big deal, just that it's a given in the world you've created. A lot of DMs I know hate wild magic, and I don't like it either. Sucks for players that crave the randomness, but on a whole I find it distracting from what's trying to be accomplished. Just be firm and consistent. Another thing most DMs don't like is flying characters...particularly at lower levels. So, while an Aarokocra may be allowed, it will be one with broken wings, or one whose wings were removed for backstory reasons.
Bottom line, write out an overview of the campaign beforehand for yourself, and maybe print a copy for your players. And, do as mentioned above: include a detail on what is available to them. I prefer not to go the route of "no this or that" and instead go with "restrict yourselves to these races/classes" as I do my guidelines. If it's new players or a campaign that won't last more than a couple months, I simply make a bunch of character sheets in advance and let them choose what they want from the pre-made options, introduce the overall gist of the campaign and get rolling.
Is there a way I can turn off specific races or class options in my campaigns yet? Or do I have to just hammer it into my players heads that in my world certain races don't exist.
Do what I do, write a one page detailing your game. Highlight the choices that are verboten for world reasons such as Warforged, Half-Elves or the like. You should also do this for all rules you have decided not to include such as Multiclassing and Feats.
This is something that should always be discussed at session 0. Also, good and courteous players should and will clear any character plans with you, the DM, before introducing the concept to the rest of the group. Worst case scenario, you just have to say "No" in front of everyone. Don't play it as a big deal, just that it's a given in the world you've created. A lot of DMs I know hate wild magic, and I don't like it either. Sucks for players that crave the randomness, but on a whole I find it distracting from what's trying to be accomplished. Just be firm and consistent. Another thing most DMs don't like is flying characters...particularly at lower levels. So, while an Aarokocra may be allowed, it will be one with broken wings, or one whose wings were removed for backstory reasons.
Bottom line, write out an overview of the campaign beforehand for yourself, and maybe print a copy for your players. And, do as mentioned above: include a detail on what is available to them. I prefer not to go the route of "no this or that" and instead go with "restrict yourselves to these races/classes" as I do my guidelines. If it's new players or a campaign that won't last more than a couple months, I simply make a bunch of character sheets in advance and let them choose what they want from the pre-made options, introduce the overall gist of the campaign and get rolling.
I think the OP means in dndbeyond. Outside of restricting by play test, Eberron, Ravnica, I don’t think there is any way to restrict content.