Bonus action spells

[Lance Tankmen]

So call me dumb but I didn't realise in the PHB it says if you cast a spell as a bonus action you can not cast any other spell unless it's a cantrip with 1 action cost. The reason I decided to read is because our cleric tried to healing word and thenjoy use spiritual weapon. He got heated when I said he couldn't as that's two bonus action's but he said he didn't use his action I said sorry no they are bonus actions for a reason that's how they want the spell's. I looked further into to to check it and that's when I saw that rule. So here's my question, the way it's worded it says when you use a spell that's a bonus action you cant cast a spell that turn unless it's a cantrip costing 1 action . So if you fireball first can you then misty step? Or is that gamey?

[Monavic]

Its all the same turn no matter the order you cast in. So casting the fireball makes it so you can not use a bonus action spell.

[Specter]

What Monavic said. But the cleric could still cast Spiritual Weapon first, then in the next turn cast an action spell and attack with the spiritual weapon, because they're not casting SW in the second turn, just using their bonus.

[90sMusic]

This is one of those rules I usually houserule over because it's a bit silly to have such a restriction. You're already bound by your spell slots, why throw another artificial limitation in on top of that?

I mean you can follow this rule and still do outrageous damage per round by being a warlock/sorcerer multiclass and using quicken spell + eldritch blast spam.
6d10+30+6d6 (for hex) every round at level 11 up to level 19. You can sacrifice all your spell slots into more sorcerer points to continuously fuel this crazy damage onslaught for a very, very long time. Alternatively, you can use scorching ray as your quickened spell and do even more damage. You go through spell slots quicker, but you do more damage.

21d6+3d10+15

To me, spell slots are their own limitation. If you blow through all your spells in one fight, yeah you'll end that fight super quick, but then in the next fight when you have no more spells... Well, I hope you like cantrips.

As for casting 2 bonus actions in a single turn... I guess it depends. The limitation on one bonus action per turn is there to prevent a sorcerer from blasting you with 10 consecutive casts of quickened spells at once and other things along that same vein. Without that limitation, you could squeeze waaay more action economy out of the game and potentially mess it up. However, personally, i'd allow using two bonus actions in a round IF they sacrificed their action to do the second bonus action. Bonus actions are usually intended to be done very quickly, taking less time than an actual action (swift action vs standard action in older editions), so logically there is absolutely no reason why you couldn't take 2 very quick actions in the same amount of time that you could've taken a quick action plus a normal action.

By the rules, you're not allowed to this, but you are encouraged to make your own rules and use common sense. This is mentioned numerous times in the PHB as well as by all of the people who actually create and work on D&D. I've heard Chris Perkins say that you aren't truly playing the game right if you aren't using at least some house rules. That's the great thing about it. It gives you the freedom to do what you want.