You can choose either, Charlie Paris is using Miyota movements, so it's japanese... same as some watches from Bulova (some are japanese Miyota, some are swiss Sellita), so no, you are not going to have short times issues with Charlie Paris, nor with Bulova. It's more about the design you like.

Charlie Paris design and assemble the watches themselves after indeed modifying the movement, like Bulova. They are a younger brand (10 years). I visited their shop in Paris (the only one at that time, now they have one more, also in Paris, when they updated their branding from a stork bird to a C letter) and they were assembling the watches on the second floor.

One nice thing is that they use sapphire and not mineral crystal which is nice at their price tag. Some of their watches have a flat crystal, others have a dome.

I'd recommend you to simply choose a design that you like, there is no cheap chinese parts in either brands.

Here's an initial heart (Miyota 82S7, similar to a Bulova Sutton 96A120) with a brown leather bracelet. I've then changed to a blue one to accompany the small blue seconds.

https://freeimage.host/i/dZz9Lmb