This was already answered, but I wanted to add more and give extra infos.
Cross posting my questions here.
1. What levels can F2P reach with secondary skills?
2. What levels can subscribers reach, primary and secondary?
3. Is it true that Vets can't use any primary or secondary skill above 75? Does that happen immediately after sub runs out, or is there a condition required for it to happen?
4. Does anyone know from which exact level players don't see /say and custom emotes from a Starter 20 anymore?
5. Is it correct that F2P can use Real ID only over the Battle.net App, not in game? And is it true that Vets can't use it at all? Sounds weird to me.
6. Can Vets reach Draenor if they own WoD?
7. Is it correct that Vets can join guilds that any own character is already a member of while unsubscribed? And that they can't deposit or withdraw items, but can deposit money?
1. Basically what Tryptozzar said. More generally, the cap on secondaries for F2Ps is either due to level requirement (level 30 or higher usually, hence the 225 caps), or by gold cost.
2. See 1, though I'm unsure if secondaries are capped by levels or not. Some higher-crafted items may have a level requirement to use, however.
3. True (and personally confirmed), and vets cannot craft items that require greater than 75 profession to craft (whether that profession is primary or secondary)
immediately when the vet's sub ends.
However, vet engineers can utilize (but not craft, unless still P2P) engineer trinkets, bombs, and other items after their subscription ends (
a full list for 101-235 engineer stuff (235 for gnomes, everyone else 225).
Same also applies to other professions: you can't make them when your sub ends, but you can still use them (with exception to enchanting. Vets cannot apply P2P enchants to their items once their sub ends.)
4. Answered, though I've yet to confirm whether the level range (for a level 20 trial) is [1, 30] or [1, 30) (that is, whether the cap includes 30 or not).
Note: the level of the trial also matters. In general, if the trial is level n, then only characters of levels anywhere in [1, n+10] {or [1, n+10)} can see that n trial's /says and custom /e. For example: level 20 characters (including 20 trials/vets) cannot see a level 9 trial's /s or custom /e, but level 18 or 19 trials (and lower) can.
5. Yes to the first question. Both unsubbed-vets and F2Ps can use Real ID (or Battletag, more commonly now) only over the battle.net app.
As for that second question, there was a bug with early 6.1 (or the vet patch) in which starter accounts could communicate to battletag/Real ID friends
in-game, but unsubbed-vets couldn't (though still could and can communicate through battle.net app, like F2Ps could and still can). This in-game bug for starters though was quickly hotfixed.
6. Yes. I saw a level 20 holy paladin in
Stormshield on my main once before my sub ended. Both mage portals and lock summons will work (though lock summons require two people to summon).
Though if a vet (including F2Ps) is looking for a place to save a hearthstone to,
Shrine of Seven Stars (if Alliance) or
Shrine of Two Moons (if Horde) in Pandaria is another consideration, as those "capitals" still (as of currently) have accessible portals to all the Alliance/Horde capitals, Shattrath, and Dalaran. Stormshield (if Alliance) or Warspear (if Horde), however, only have a portal to Stormwind/Orgrimmar.
7. Yes to the first question. That vet can even communicate through /guild chat, much like F2Ps through /f2ptwink with the F2PAddon. And they can't withdraw items or gold, though I too am unsure if they can deposit money or not.