Unsure of what movement to use? Here's a simple explanation of their differences. You can watch this Video for reference.
38 mm size is comfortable yet the case accommodates Seiko sea urchin dial in good proportion. Also the case looks well with W&S straight end FKM rubber strap in my opinion.
Don’t hesitate to deal with them, they’re amazing with customer service and their parts are really nicely finished and have a premium feel to them