Here's the big question I have. How much should I care about matching components?

I'm currently using full mechanical Ultegra, and I want to switch over to Sram Etap. If I switch everything except for my crank, will my bike look stupid?

Same question for wheels. I want to add a full disc wheel to my setup, but the brand of wheels I use doesn't make a disc. Once again my bike will have miss matching parts.

Thoughts???

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I am a bad runner.
I met Javier Gomez once.
I don't speak in miles.
I have opinions.