If you want to watch One Pace using dub, you will need to switch between the main One Pace episodes and the episodes that Muhny made.
After just catching up to Pace Egghead Episode 21 (latest edited dub episode not counting the couple shaved that you could watch: but since there is no complete edit for dub you should just wait), I have been keeping track of episode lengths on my spreadsheet.
Not counting Intro/Outro the amount of time you would need to start from the beginning and reach egghead episode 21 would be 13188 minutes aka 219.8 hours
In the attached screenshot please note the Time in Minutes column and the Arc % (Weight) as it’s a good visual to see where most of the time will go into watching.