IMO whoever told you not to use a process lens was badly misinformed. Process lenses are ideal for enlarging as they are designed to photograph flat objects and are apochromatic. Commercially I have used process lenses from 240mm to 1200mm focal length for enlarging. One difference is the reproduction ratio range that the lens is optimized for. Process lenses are commonly used for magnifications from 1:1 to 1:3 but will do an amazing job outside that range. Different lens designs will be optimized for various magnification ranges.
Buy the 135mm lens first. Test a 6 x 9 negative with it and you might not need a 105mm depending on you enlarger and setup.
Your middle lens is an enlarging lens. It could be used as a process lens but it only has a 50mm focal length so would be totally impractical to use as such.
Have fun.