I only buy the bullet proof parts for my guns but since you’re tinkering and learning with a $300 Tisas, I’d buy the cast parts. Not quite as good as the bullet proof but still good parts and for what your doing easier when the aw crap moment happens.

 

Smart thinking.

 

For things like disconnector, for example, their standard part is plenty good enough. Grip safety too. For a heavy wear part, like a hammer or a slide stop, I would use either their bullet proof parts or an EGW part, whichever looked nicer for that build.
I have a couple of "bullet proof" thumb safeties and a couple of their standard ones, and once fitted, I cannot tell the difference.

 

Personally I would avoid a cast part for anything you might have to significantly file and fit. Mainly because you might run into a casting bubble which could be cosmetically unsightly and even potentially weaken the part depending on the location and interaction with other parts.

That said, if you did run into that issue, buying a second part probably wouldn’t be that painful to the wallet.

 

I'd go cheapest possible for just ease of mind when grinding on it. What is the point of stressing out about f'ing up a part when you are trying to have fun and learn. I am a hard believer that it is good to learn when you go too far.

But as mentioned above, EGW, Ed Brown and Nighthawk are also good alternatives. If you set on milled parts, then price checking between those 3 would save you some money. Milled EGW grip safety appears to be ~20 bucks cheaper.

 

I Don't know your time frames. I try to buy parts during the Christmas season on sale at discounted pricing. Another avenue to consider is picking up pulls that show up in the classifieds. I'm sure everyone here has a parts bin of stuff for a rainy day project.

Tisas. They are not MIM inside. Now some polishing, stoning takes on whatever steel they are using. I cleaned up the 9mm Aviator with just polishing, tweaking the sear spring and replacing a trigger. The slide stop along with the thumb safety, mag release just dropped in. I added a EGW flat wire recoil, the rest are all Wilson BP parts. It feels in hand more like my other pistols. The sights were adequate but I needed more air on the rear. Replaced with a 10-8 NM and a Nighthawk Gold Bead. Herters grips picked up from a member here, Long story. Go have fun with it. Look at it like this. The worse thing you may have to do is buy a replacement part. One important thing I do is set a parts budget of what I'm going to spend. A rule of Thumb is about doubling the cost of the gun. Checked that box....

 

Don't buy a Wilson Compound Radius grip safety for your first grip safety fit.

 

You went with a low cost gun to learn with. Stay with low cost parts until you feel confident.

 

I need Wilson to hurry up with the rounded full size blued MSH/magwells, they’ve been out of stock forever