When showing off garments in Hubs, the backside is usually not visible. Some exports are one-sided, but if you have a cloth with two sides, here is a workflow that allows you to remove the inside and all geometry based seams. The latter require a ridiculous amount of vertices and are thus better baked into the cloth texture. When both the outside and inside of your garment are blue when turning on Face Orientation in the viewport overlays, it has an inside you can remove to save space and performance.
The idea is to go into edit mode, deselect everything by clicking an emtpy area and the hover over a part you want to keep and use the shortcut L to select all connecting geometry. Since cloth is made of several individual pieces of cloth sewn together, this will select exactly one of those pieces. Repeat this until all parts you want to keep are selected. It works pretty well in edge select mode.
Having all patches that should stay selected use CTRL+I to invert the selction, the P to separate the now selected parts from the object. You should now see the separted part tinted in red because we look directly at the backside of the interior faces. Go back to object mode and move the newly separated object to a backup collection that is turned off. That way you can always come back in case you have removed a little too much from your garment.
In this example, removing the inside and the seams resulted in a reduction from 1.257.400 faces to a mere 23.821 which is a considerable reduction.