You can avoid creating system reserved partition. But it's not easy.. Also it works only if you create new partition using setup wizard - this mean, if you leave HDD unpartitioned, system reserved partition will be still there.
Original method can be found here, needed patches here, and reopened here for Windows 7.
Inside boot.wim image 2 (Windows setup) locate winsetup.dll. This file have responsible code inside. We are looking to function Callback_Createpartition that needs to be patched.
This is tested for Windows 10 20H2 (10.0.19041.630). Open file winsetup.dll in HEX Editor, locate offset 10E3CA and change 0F 84 to 90 E9. Thanks abbodi86 for transplanting Windows 7 winsetup.dll patch to Windows 10.
In different file version it should be located on different places. I have no idea how to patch it dynamically as it's not mu cup of tea. Maybe nuhi can do it as nLite have some patches, like uxtheme.dll
i would leave it at 100mb, you never know if you will want to set up a dual or triple boot later on and end up in crap creek because you set it too small. if you know you'll never dual/triple boot then go for it my boy hahaha. i personally prefer to install in isolation on different drives and use the bios boot menu.