SCHX
Schwab U.S. Large- Cap ETF
stock NYSE ETF

SPYM(S&P 500), SCHX(S&P 500+),SCHB(US Broad Market), VXUS(total international),VEA(international developed markets)

The problem with VTI, in my view, is that it is only 10% small-caps.
Of those small-caps, half of them are small-cap growth, and half of them are small-cap value. Small-cap value has historically outperformed the market. Small-cap growth has historically underperformed the market. So they almost cancel each other out.
AVUV is an ETF that is strictly small-cap value.
So combining VOO + SPMO + AVUV would give you Large-Cap Growth/Value + Small-Cap Value. Which is a pretty diversified US portfolio.
If you wanted to be slightly more diversified and include Mid-Caps, you could replace VOO with SCHX (like VOO, but top 750) or SCHK (top 1000), but it wouldn't matter much I don't think.
As far as moving together, value (AVUV) and momentum (SPMO) tend to move independently of each other. Not all the time obviously. In a big crash, everything might fall, but one or the other will probably rise from the ashes much faster than the other.

VOO is \~88% of VTI, the extra total US in VTI does not come out to be that much. SCHX has more than 500 companies, SCHB has a few thousand less than VTI but both are identical. I prefer SCHB for its lower share price.

SCHX is another one you might want to consider instead of SCHB. That’s if you wanna keep Avuv small cap value ETF. SCHX Holds approximately **750 of the largest U.S. companies** in the U.S. market.

Please buy some VOO. SCHW SCHX.