Prepare the subfloor
Everything visible depends on what's underneath.
Moisture nobody tested for, a slab nobody levelled, and an installer who carried on regardless.
The subfloor decides the outcome. Unevenness telegraphs through tile and vinyl alike, and moisture in a slab lifts adhesive and cups wood months after everyone has been paid.
Manufacturers know this, which is why their instructions specify testing and tolerances — and why warranties are void when those are skipped. Following them is unglamorous and it's the whole job.
Preparation should also be priced honestly. Quoting installation cheaply and discovering the preparation afterwards is a common tactic; itemising it up front means you can compare quotes properly.
Everything visible depends on what's underneath.
It's what keeps the warranty alive.
So quotes can be compared honestly.
Free, with an itemised written quote and no obligation.