While the gravitational impact of such a big 4th planet on Earth would indeed be negligible, let's check why that super-Mars was allowed to be that big.
Mars actually should be much bigger than it is - the amount of material found at 1.5 AU should even have been greater than at 1 AU. Of course, at 1.5 AU there was less iron and more silicates, so Mars should be at least rivaling Earth with its size. According to Grand Tack hypothesis it isn't the case because Jupiter formed much closer than it's today - at about 3.5 AU and migrated inward stopping at about 1.5 AU then receded because of tug from Saturn. Jupiter's formation must have been rather quick - it had to acquire its hydrogen and helium before they were swept away by solar wind. So early in Solar System's history there is a planet that sweeps the most of material from Mars' orbit and compresses much of it at about Earth's orbit.
So, to allow super Mars, we must remove (or at least severely cripple) Jupiter. Then indeed, with all this material in place we could have 4th planet even bigger then Earth but perhaps lighter. However, that means that there is no condensed band of material at 1 AU - it is more evenly dispersed thorough inner system. It isn't to say that Earth wouldn't form - actually the state of Solar System after those ~4.6 billions of years without Jupiter would be very different in unpredictable ways. We don't know how much planetesimals would form if not Jovian sweep through young system, how much would avoid spiraling into the Sun, how would they collide and when they mostly stop colliding (so that life could evolve significantly).
And conversely: would ice giants later sweep through outer disk regions if not Jupiter's influence? In our timeline (as reconstructed in Nice model) it caused Late Heavy Bombardment - should it happen in our hypothetical scenario, there would be no Jupiter to protect us. But without Jupiter, there could be nothing to prevent Saturn accumulating more and more matter and possibly become a specimen of "hot jupiters".
I'm trying to say that when asking such questions we just can't consider only static, present situation. We should check how could such situation come into existence and - as you can see - once we begin to do that, we quickly enter the realm of wild speculations, too broad for a sensible answer.
TL;DR: after removing/diminishing Jupiter and enlarging Mars, any Earth orbit (or no Earth orbit) and asteroid belt are possible. I doubt though if an asteroid belt could form if there was a massive planet nearby enough to be able to draw asteroids from the belt.