Does this work or am I getting the rules wrong

Quote from SmiteMakesRight_3_5 >>

Quote from Tana___ >>

And, technically, potions of speed stack with Haste (As they say that you gain the effect of haste, not cast the spell, meaning that it stacks)

That is dubious and I think Combining Spell Effects is clearly intended to apply preventing them from stacking.

However, keep in mind that the effect is triggered off of casting a spell with a spell slot, so that could be a Bonus Action spell, such as Expeditious Retreat. (It could also be to cast Haste or Prismatic Wall in order to get an extra Dash!)

Still, four actions plus a Bonus Action is, pun intended, wild.

 Except your not casting a spell, you're drinking a potion. The spell has nothing to do with it, other than the effects

Quote from Tana___ >>

Quote from SmiteMakesRight_3_5 >>

Quote from Tana___ >>

And, technically, potions of speed stack with Haste (As they say that you gain the effect of haste, not cast the spell, meaning that it stacks)

That is dubious and I think Combining Spell Effects is clearly intended to apply preventing them from stacking.

However, keep in mind that the effect is triggered off of casting a spell with a spell slot, so that could be a Bonus Action spell, such as Expeditious Retreat. (It could also be to cast Haste or Prismatic Wall in order to get an extra Dash!)

Still, four actions plus a Bonus Action is, pun intended, wild.

 Except your not casting a spell, you're drinking a potion. The spell has nothing to do with it, other than the effects

 There's a SAC answer that addresses the intent:

Do the benefits from Bardic Inspiration and the Guidance spell stack? Can they be applied to the same roll?

Yes, different effects stack if they don’t have the same name. If a creature under the effects of a Guidance spell makes an ability check using the skill chosen as part of the spell’s casting and also has a Bardic Inspiration die, it can roll both 1d4 and 1d6 if it so chooses.

Yeah but reading this as an indication that different effects with the same name can't stack is a bit of a logical fallacy.
"A implies B" doesn't mean that "not B implies not A".

Yeah... it could be. I agree with SmiteMakesRight_3_5 in any case.

To be honest, so do I. I can't shake that little sliver of doubt, but it's hard to find conclusive arguments for the other way around...

Quote from Tarod_ >>

 There's a SAC answer that addresses the intent:

Do the benefits from Bardic Inspiration and the Guidance spell stack? Can they be applied to the same roll?

Yes, different effects stack if they don’t have the same name. If a creature under the effects of a Guidance spell makes an ability check using the skill chosen as part of the spell’s casting and also has a Bardic Inspiration die, it can roll both 1d4 and 1d6 if it so chooses.

Yea and then there is this one too:

Do the AC bonuses from a Ring of Protection and Bracers of Defense stack?

Yes. In general, bonuses stack unless the text explicitly says otherwise (such as effects from the same spell). For instance, you can’t benefit from more than one Ring of Protection, because the text says you can’t attune to more than one copy of an item at a time.

It seems like kind of a missed opportunity to have two answers about this when both names effects clearly similar but also clearly different. It would have been great if they could have cleared up Potions instead as the language for those is a lot less clear.

Potions generally come in four varieties. 
#1is potions that just gives you an effect, like Potion of Climbing that says "you gain a Climb Speed equal to your Speed for 1 hour" (and some add-ons). Clearly not going to be a problem here.

#2 is Potion of Animal Friendship that says "you can cast the level 3 version of the Animal Friendship spell". A bit weird wording but also clearly affected by the two SAC answers, it won't stack (not that there is anything to stack but still).

#3 is Potion of Heroism that says "you are under the effect of the Bless spell". Also not an issue, clearly a spell effect so it won't stack.

#4 is the majority though and here comes the problem. Spells like Potion of Speed that says "you gain the effect of the Haste spell for 1 minute" (there is a bunch of these that gives out the effect from different spells).

I think that the intention is for these to be viewed as the same as if you had gotten the effect by having the spell cast on you. But I also think that a lot of people views something you get from a potion as different to something you get from a spell (especially as, to me at least, it seems like many of these are written as they are just so that they didn't have to write up a "new" effect from the potion but rather just could re-use an already existing game mechanic).