For sorcerer points, like heightend or twinned, can you only choose one per round or both? 

You can use only one Metamagic option on a spell when you cast it, unless otherwise noted.

Only Empowered Spell has the option to be used with another metamagic feature.

To further clarify, you can use as many as you have actions in a round to cast different spells. For example, you could use quicken spell to cast a 1 action spell of any level as a bonus action (say scorching ray), then as an action you could cast a twinned Firebolt cantrip. So 3 scorching ray bolts and then 2 more firebolts... ouch. If you have warcaster, you could totally use another sorcery point later in the round on someone else's turn to pump up a AoO it grants.
The limit is based on per spell not per turn or round.

Quicken is great when paired with cantrips since it is cheap.
You could twin a shocking grasp. Hit two people threatening you in melee, they no longer get reactions. Move away, then fire off a quickened ranged spell as a bonus action

I had a similar question to this and it was how would it work if i multiclassed.

for example how would a bard fighter sorcerer work.

How many times could i cast vicious mockery? Using action surge and sorcery points.

In my head it would be (roughly) 5 times

Quote from Cjgamez777 >>

How many times could i cast vicious mockery? Using action surge and sorcery points.

At most 3 in a single turn. First when using Quickened metamagic as a Bonus Action. Second when using your normal Action. Third when using the Action Surge Action.

I have no idea how you came to the number 5. Even if Action Surge gave you another Bonus Action (which it doesn't) it still wouldn't get to 5.

You could maybe get a 4th in the same round (but not the same turn as the other spells due to Bonus Action Casting rule) if you had the Warcaster Feat and cast it as an opportunity attack - but you can never guarantee that you'll get the chance.

Actually you can twin it twice with action surge and use a quickened bonus action one. 5 is correct. 

Quote from dot113 >>

Actually you can twin it twice with action surge and use a quickened bonus action one. 5 is correct. 

Twinning doesn't cast a spell twice. It casts it once with two targets. There is a difference.

Quote from Emmber >>

Quote from dot113 >>

Actually you can twin it twice with action surge and use a quickened bonus action one. 5 is correct. 

Twinning doesn't cast a spell twice. It casts it once with two targets. There is a difference.

 This is technically correct, but the "effective" number of targets would be 5 (one quickened, 1 normal (twinned for 2 targets), 1 action surge (twinned for two targets).  That is assuming you don't have a harsh DM that rules that the "a cantrip..." in the Bonus Action Spellcasting rule means "1 cantrip only" (I personally rule it doesn't)

Quote from iconarising >>

Quote from Emmber >>

Quote from dot113 >>

Actually you can twin it twice with action surge and use a quickened bonus action one. 5 is correct. 

Twinning doesn't cast a spell twice. It casts it once with two targets. There is a difference.

 This is technically correct, but the "effective" number of targets would be 5 (one quickened, 1 normal (twinned for 2 targets), 1 action surge (twinned for two targets).  That is assuming you don't have a harsh DM that rules that the "a cantrip..." in the Bonus Action Spellcasting rule means "1 cantrip only" (I personally rule it doesn't)

Technically correct is the best kind. ; )
I was very specific because they asked how many times they could cast it - not how many targets they could hit.

Quote from Emmber >>

Quote from dot113 >>

Actually you can twin it twice with action surge and use a quickened bonus action one. 5 is correct. 

Twinning doesn't cast a spell twice. It casts it once with two targets. There is a difference.

True :) 

Thank you I've been trying to find this rule forever!

Quote from TolkienAsian >>

Thank you I've been trying to find this rule forever!

 Just be aware: some rules mentioned in the thread have new restrictions if you're using the 2024 rules. For example:

Quickened Spell

[...] You can’t modify a spell in this way if you’ve already cast a level 1+ spell on the current turn, nor can you cast a level 1+ spell on this turn after modifying a spell in this way.

And:

Level 2: Action Surge

[...] On your turn, you can take one additional action, except the Magic action.