@MyBrainHurts
There are two aspects to your post.
1) You want to reduce the columns in order to avoid all the Data transfer/performance to your app.
2) You want to only display certain columns of information in your gallery.
For #1 - there is no way to do this. PowerApps will always return all the columns. If you use them or not, they are always returned. You might hear some say "Use ShowColumns", but ShowColumns will still internally retrieve ALL of the column data. So you cannot avoid it.
For #2 - this is just about statements in your labels and such to display the chosen columns.
Please clarify what you are looking for if this does not resolve what you need.
I hope this is helpful for you.
