Walk-in shower water to Soaking tub

[BosRamG]

Bathroom currently has walk-in shower. I would like to install free standing soaking tub. Supply line. From basement 3/4 Pex-B Tees of to 1/2 PEX-B runs to walk in shower. How much pressure or flow rate drop will occur if I tapped 1/2in line from walk-in shower to tub vs cutting drywall in living room finding 3/4in line refitting 1/2in line to walk-in shower to 3/4 line then Teeing to two 1/2in lines shower and tub. Access shower plumbing is easy with doors compared to cutting drywall and looking for original line somewhere in living room. Other Tee line goes from 3/4in line from basement tees off 3/4 to 1/2 with goes to 2 sink vanity. Will all extra cutting refitting gonna make significant difference. Probably would not use tub and shower at same time frequently but it would happen every now and then.