If you know the width and the offset, you can calculate the backspace fairly accurately. Online info for the stock wheels on my 2015 show 6.5Jx16 ET50, which calculates out to 5.2185" backspace. But the website shows backspace of 133mm (5.2362 inches), web link here. Slightly under two-hundredths of a difference.
Positive offset pulls the wheel in, negative offset pushes it out of the fender. You're moving them out 5mm/0.2" (+50 vs +45), but the wheels are also a full inch wider overall than stock, so the inside edge will be about 0.3" inward of stock (half the difference in wheel width, minus the 0.2" change in offset going outward). I think you'll find that you'll be going in a slightly straighter line with those wheels and the reduced steering angle. Then it's up to you, Old School, to decide if the reduced angle is acceptable or if you want to try some thin spacers (quarter-inch would nearly bring the inside wheel edge back to stock location) or whatever. Problem there is that the wheels would then be sticking a full inch out from stock location, not accounting for any tire width difference added on.