If you’re bragging about how much you can lift to people who don’t lift, not at all. If someone asks me how much I deadlift when I’m bragging to them about how strong I am I just add 100lbs to my straight bar deadlift and use that number. Trust me, they’ll be none the wiser and considerably more impressed with you as a person.
Not necessary at all, unless someone starts calling you out on your numbers when you’re bragging about how strong you are to people. Then you need to start adding in qualifiers. “Yeah I deadlifted 800lbs. It was with reverse bands and off of blocks on the trap bar with high handles and straps and my training protocol doesn’t involve locking it out. It was dead on the floor to start though, so it’s a deadlift. You don’t know what you’re talking about broseph.”
Things can get tricky if they call you out at the gym or somewhere else where you might be expected to duplicate the feat you’ve described. Luckily you can always fake an injury to get out of this. Start with saying you messed up you knees, then you can rotate different body parts in to keep the excuses fresh. Hips, back and shoulders are always good body parts to claim injury on. Just make sure there isn’t a safety squat bar around if you’re claiming you can’t squat because you can’t get your shoulders into position anymore. Trust me, that can get awkward.
Hope this helps. Don’t just dream about talking about how much you can lift. Get out there and do it!