Pulling new images works exactly the same for navcontainerhelper as it does for plain Docker; there's no special command there. However, you can specify -alwaysPull as a parameter for your New-NavContainer command, which will –as the name clearly implies –always try to pull a new image version before running your container.
But navcontainerhelper actually adds more convenient optimizations automatically. If you do not specify ltsc2016or ltsc2019as part of your tag, it will determine the best container platform and use that. It also automatically determines whether process isolation is possible and sets the memory limit, if necessary, to 4 GB.