The opening strength will only work when you know how to exploit something small in opponent's opening like a miss of tempo or wrong reply, which I think is above the skill of sub 1700. All the players above 1000 know basic principles like mobility of pieces and developing centre.

> The opening strength will only work when you know how to exploit something small in opponent's opening like a miss of tempo or wrong reply

That's exactly what I am saying. If one person knows the strength of an opening and the other person don't then the person who knows the opening has a clear advantage. I agree with @skulk's argument though - the time is better spent on learning tactics and analyzing games over learning many opening given the player is sticking to some particular openings.

> the opening has a clear advantage

not exactly if the person can't use the slight advantage for their benefit. They only have window of 2-3 moves at max to exploit less developed pieces else the advantage fades away(assuming non point positional advantage). It is hard for 1700s to exploit very minor advantage and most of the time the win is due to a blunder by opponent.

What I said was conditioned on player sticking to few opening that s/he knows very well. It not hard to convert the advantage to a win, and it's also not obvious that some move is a blunder until after it becomes obvious.

1700 rating is not very clearly defined since different Chess websites uses different ranking system and the rating can vary dramatically. For example, on average there are 400 points difference between chess.com and lichess.com ranking.

The amount of opening preparation that's useful for a sub-1700 is minimal; diminishing returns due to not understanding middlegame positional ideas and shaky tactics hit really hard. When I was really into chess as a kid ~15 years ago, I spent a ton of time reading opening preparation but it was definitely time that I should have spent simply analyzing high level play in all stages of the game because my opponents either didn't know the theory (so while they technically deviated into "worse" lines, I had no hope of understanding why they are "worse" in the general case) or more rarely, they know how to avoid common theory.

I think the most important opening prep for a novice is learning what lines to avoid at all costs. A lot of this, though, can be established with the basics: develop pieces, castle early, control center. Any time your opponent tempts you into violating any of these, think thrice.

I disagree. If there are two 1700 players, the opening player is only better if the game goes according to the prepared moves. A good tactical player who realizes you are going via prep will make a stupid move and pull you out of book. From this point on the tactical player has the advantage because he has experience defending random stuff, while the opening player has to figure out why the move so stupid it isn't even in his book is bad and exploit that. Of course if the stupid move is in the opening book then the opening player is better, but that is unlikely.

> A good tactical player who realizes you are going via prep will make a stupid move and pull you out of book.

That only works against a badly prepared player. Learning an opening isn't just about memorising moves, it is also about understanding why the moves -- both your own and your opponent's -- are good. If you have studied an opening well, you will understand why a stupid move is stupid and be able to punish it. Of course you may still end up messing things up and lose the game later on, but you should be able to emerge from the opening with an advantage.

> pull you out of book.

Openings do not necessary break here. They are meant to take advantage of a situation by a series of branched off movement. If you are not making good enough guess about why a particular opening is played - making one move to pull somebody out of the book won't do much good.