Trews or Tartan Trousers: Similarities or Differences?

[Braw Cathairneach]

I may need to forgo my kilt for trews. ‘tis been close to a half-century since I competed in hunter/jumper events, therefore the traditional military fishback trews are unlikely to accommodate my stout frame.

Can anyone opine or recommend trews options? How odd might it appear to wear tartan trousers with kilt jackets vis-à-vis traditional fishback military trews?

Any ideas who makes trews? It seems that not every kilt maker makes these things. Measuring for them seems a bit tricky if done by the purchaser and not the vendor.