Who's to say the business that issued the ticket will accept your homemade imitation? with "adjustable styles, images, colors, and text fields"?

Absolutely no one whose job it is to scan barcodes gets paid enough to give a single fuck about how that barcode was created

There's some places like railroads that I've seen care about this so that people don't share tickets (like monthly pass types)

I use Pass4Wallet for several loyalty/gym memberships.

In my experience, if the code scans, the code scans.

It works fine if scanned by a machine though (ticket gate, self checkout etc.)

I've used a third party app for this for a UK weekly pass train ticket you could only buy physically, but if you buy it on a train rather than at a station they can't print you a ticket with a magnetic strip and they have to give you one with a barcode (technically an Aztec code), which you can then scan onto your phone and use at the gate. But I kept the original ticket with me too and would use that if a person asked to inspect it