Hello @Pratike6 This is mostly on preference, What I do first is determine how large of bag I have for pressing, If it’s the size of an X-1, I remove the green crown from pineapples, quarter then and place it directly into the press, You sacrifice a small amount on yield, but make up for it with time and labor, I find little to no change for flavor and color.
For smaller cold-press units I would cut the pineapple down to fit the machine, cut and press with peel still on, this helps since pineapples are quite mushy.
For citrus, I always leave peels on lemons and limes, put directly into the press, and process, I actually prefer the flavor than grinding peeled citrus and pressing.
For oranges and grapefruit, I always peel, then process.
On rare occasion If I had an X-1, I would close the press the width of a halved orange or grapefruit, drop them in unpeeled and press, the bitterness is from the juice passing over the pith, this technique reduces it, however this also only work on about 50% of the varieties of oranges and grapefruits. Hope that helps.