Fenix 6S Pro vs Forerunner 945 vs Forerunner 745

Hello, I am looking to purchase my first Garmin watch, I mainly swim (daily - pool swimming and open water)  but sometimes outdoor walks/hikes. I have small wrists and have been thinking of going for the Garmin Fenix 6S Pro, but am concerned it will be too heavy for daily swimming. Therefore have also been looking at the FR745 (for size) but due to price, if going for a FR seems logical to go for a FR945.

Ultimately I like the Fenix series, also because it is more than just a training watch and looks fab for every day use. just concerned about weight.

Please may I ask for any advice from people who have tried/tested and know a little more than me! Thank you.