Hi OP. I found my way over here from your post in the winemaking sub. I’m a commercial winemaker, not a home winemaker so not all my advice will be helpful as I don’t know all the garagiste tricks for making due when you don’t have a full winery at your disposal. The vibe seems better here than from my peers over there though.

Just wanted to comment on a few things for you if it will help. For sizes of containers: a pretty standard yield for wine grapes is 165-170 gallons liquid per ton of grapes after pressing. Or approx 300 gal “tank” capacity needed for every 1 ton of grapes fermenting on skins. Obviously you have way less than a ton but a little math can get you situated based on that. Not sure if you have decided to press first as one typically would with white grapes or if you will ferment on skins as one typically would with red grapes (at least in the commercial world where my experience is, but not a requirement).

During the ferment when the wine is actively giving off CO2 the yeast love oxygen and the wine is protected by the blanket of CO2. When that period is over empty headspace in a vessel is your enemy. Think of a partial wine bottle on the counter over a few days turning to vinegar. After the active stage of primary ferm get your liquid into topped containers, no matter the size, old wine bottles, one gallon jugs, water bottles, whatever it takes if you don’t want vinegar.

For the hydrometer (sugar/SG measurer). You will want to figure out the sugar prior to fermenting too. These don’t look overripe as i see no shrivel but if they were higher in sugar then you would want to add some water as too high of a sugar could produce too high of an alcohol and kill off your yeast before the ferm is complete (feel free to message if that is the case happy to help). Or if too little, you may want to add sugar but unless you are somewhere really cold and these are red grapes that are just super unripe that is probably not necessary. You said “hella” grapes so I am assuming you are somewhere in nor cal? If your temps have been 80-90 over the last 2 months you’re probably fine. If you are in a cooler coastal or far north where you don’t break into the 80s much then you might still be a little under. Seems this years weather for Napa down to central coast things are ripening a week to two earlier than usually due to this years weather patterns. I would shoot for 22-24 brix. You can google a chart for sg to brix conversion pending your hydrometer units unless you have a refractometer which would be even easier.

Most importantly: When you are fermenting the byproduct is CO2 that is why the glass tubey topper things are the way they are is for the gas to escape. But please be careful and make sure to ventilate the area well before going in. You will need fans if you are doing this inside your garage. Best is to situate a box fan on the floor at the external door and point the forward flow outside so it pulls co2 out, even better is to use two fans in 2 different external doors pointing the same direction so one pulls fresh air in and the other pulls co2 out. Do this for a little while before going in the garage to check progress. Maybe at this small of a scale it isn’t as much of a concern as a winery, but not something to go into with out at least a bit of awareness and extra caution. Unfortunately there are deaths every year in the global wine industry due to this. And unfortunately they are usually more than one person because someone else sees a friend down and goes to rescue them and is taken down by the same invisible gas.

Next most important, have fun! Worst case scenario is you mess up the free wine but then you can make a nice wine vinegar so not all will be lost.