I always go 5 new letters for the second guess and usually for the third. Knowing more letters are in or out is a lot more information than finding out the same letter isn't in a second position. Particularly for Quordle, you really want more letters through three or even four guesses.
Yes, in Quordle you're compelled to use a standard opening. Regardless of what you learn from early guesses, no followup can be more informative than just querying more letters.
It's kind of disappointing to me how much luck is involved in Quordle. I've just established that the only common letters in a word are S, A, and Y, with A second and Y fifth. All three other words are already guessed. Do I guess SASSY or SAVVY? The game gives the appearance of being much more skill-based than it actually is.
But I've found the same applied with Quordle. Recently I had _LARE and even that allows FLARE, GLARE and BLARE. It turns out solving another word (BRINE) eliminated one of the options for free.
I've noticed whoever chooses the word of the day for Worlde likes these types of words. Like I've ended up with S_ILL before leaving SPILL, SKILL, STILL and SHILL.
Josh Wardle said on a podcast[1] that him and his partner chose the set of words by taking all 5 letter words in the dictionary and filtering out the "bogus" ones. He then randomized the order of these words so that him and his partner could play. However, I'm not sure if the New York Times has changed how word selection works.
[1] https://syntax.fm/show/430/creator-of-wordle-josh-wardle
This advice applies much better to Wordle than it does to Quordle, though. Quordle gives you nine guesses. Four of them are already taken by the need to provide four answers. Three or four go to your fixed opener. That leaves you either one or two discretionary guesses. If your opener ended up giving you trouble with more than one word, you're basically hosed.
My 9yo loves Quordle also but usually starts TREAD and MINOS.
I'm vaguely tempted to take the dictionary and figure out an optimal strategy that 1) guarantees success and 2) minimizes the number of guesses. If you assume every word is equally possible (it isn't; they're manually chosen) there would be an optimal starting word. I'm sure others have looked into this but this is something I'd like to do myself.
After that it branches depending on what hits you get on that first word. It may be possible that a second fixed word (or a small set of second words easily memorized) would be near-optimal but not actually optimal. I'd be curious to know this too.
But I'm curious how good an optimal strategy would be vs some of the naive strategies we've all chosen.
It's also an interesting question as to when it's worth switching from finding what letters are in the word vs locking down their position. If you get COAST and AT are in the word but in the wrong position, should your next attempt be 5 new letters or a word containing AT in different positions? The disadvantage of this of course is you're only testing 3 new letters.
I also toy around with Quordle where you have 9 guesses to find 4 words. That one's harder and the strategy is a little different. There I've pretty much settled on finding a set of 3 words that covers all vowels (and Y) and 9 of the most common consonants.