I have subbed to play Classic a few times since its release but haven’t played retail since MoP.
I was at the page to purchase TWW reviewing the options and I noticed the highest option (Epic Edition, $80) had 30 days of game time.
Does this mean that if I buy the game using the base edition purchase of $50, I will not be able to play without paying an additional and immediate sub fee?
Yes. But I’m not sure I understood what you’re asking, so just in case, here’s the long version:
To play either Cl;assic or Retail, you must have Gametime/Subscription. Always. (Except for the Free Starter Edition where you can play Retail only up to level 20.)
The same Gametime/Subscription will work for both Classic and Retail. Once you have your gametime, you can play either or both.
You must have bought the most recent Retail expansion if you want to play it. When TWW launches, you can still play anything up to Dragonflight on gametime alone, but you can’t get into TWW without also buyiing TWW.
Buying TWW doesn’t get you gametime, so you need to buy both gametime and TWW to play TWW.
TWW Epic edition includes 30 days of gametime, so if you buy Epic edition, you can play TWW for 30 days; after that, you need to buy more gametime or have a subscription.
If you buy TWW base edition, you will not be able to play it unless you also have bought gametime or a subscription.
Thanks for the info, that answered my question.
Do you happen to know if that 30 days of gametime will apply now if I purchase, or at the start of TWW?
When you buy gametime, whether directly or as part of a TWW package, that gametime will be applied immediately, within hours at most.
If you already have some gametime, and buy more, that extra gametime will be applied as soon as your existing gametime runs out.
Sounds good, thanks again.
I was just reading up on MoP remix, now I suppose I should decide whether it’s better to start retail now or wait until next week when MoP drops.
I am a pretty casual wow player, mostly I sub in 1-2 months a year and play for a few weeks. Would it be better to go for the base game or wait a week and play through the MoP remix?
With MoP Remix, you MUST make a new character, which will start at level 10 in Remix, and after Remix will become a “real” character in regular Retail WoW on the same realm where you created it.
If you want to revisit and level your old characters, Remix won’t do that for you, so you would want to buy TWW and play regular retail WoW to level them to prepare for TWW.
That’s the only relevant factor I see. It’s up to you. 
I’ll just add that if you currently have a subscription(as opposed to game time) when you add 30 days game time, it will push your next renewal date to 30 days later.
The main reason to buy TWW now is if you don’t have Dragonflight and want to play that content now. (It’s a better deal if you know you will play TWW than just buying Dragonflight.) If all you want to do is MoP Remix, you don’t need Dragonflight, so I’d hold off on buying.
Ok, good information all around thank you.