@OP. I would brush up on the Sunny 16 rule and maybe consider using a yellow or CPL filter.
Or have a look at the ultimate exposure calculator too.
For 35mm format use (and the reduced control over when the film is exposed given there are 24->40 odd exposures to get through), the appeal of 400 speed film (to me) is versatility.
I can use it full sun - 1/250, f/11 as a start point (1/1000 gives you f/5.6, stick an ND 0.9 (ie; 3 stop) filter on would give you f/2.8, 1/1000 which is pretty 'wide open' in full midday sun imo (and would look it.)
Full shade is going to be 4 stops down. Most times you'd be adjusting in the middle depending on what you're exposing for.
I can't avoid full sun as I'd hardly get a chance to take pictures!
But 400 speed film is far more convenient (to me) so I can just 'point & shoot' at f/8->f/16 but also handle when the light gets lower right down to indoor evening just pushing the shutter speed (and aperture) right out. It also means other B&W filters, such as orange, green and yellow-green are easy to throw on when the situation calls for it.
Right now I've got a roll of 100 speed Ektar 'stuck' in my camera which is going to be a hassle when I go out this evening, f/1.4 lens or not.
If 100 speed film is working for you, I'd stick with it. I'm not one for shooting 'wide open or wider (??!!)' in general and use ND or colour filters to manipulate aperture if I really need to.
Better still, buy more 35mm cameras, 100EI, 400EI, positive, colour negative etc.. can never have too many! 😀