The FUD is that TPS is what matters. A transaction could be anything from a single payment to a massive coinjoin. Usable capacity should be measured in terms of transfers rather than transactions.

If we define a coin transfer as spending one coin and creating one new coin, then the coin transfer capacity is roughly:

1000000 / 600 / (input_vsize + output_vsize) coin transfers per second

Assuming all P2WPKH, that's:

1000000 / 600 / (68 + 31) = 16.8 ctps

And assuming all Taproot:

1000000 / 600 / (57.5 + 43) = 16.6 ctps

That is the on-chain transfer capacity if we assume a constant UTXO set size.

In the future, full-aggregation CISA can save up to 16 vB per input, giving:

1000000 / 600 / (57.5 - 16 + 43) = 19.7 ctps

For getting new users into Bitcoin, the real limit is the rate at which new UTXOs can be made. The size of a Taproot or P2WSH output, such as that needed for a Lightning channel, is 43 vB. Thus the limit for the number of outputs per second is:

1000000 / 600 / 43 = 38.8 outputs per second

Input/output sizes from Bitcoin Optech Transaction size calculator