I'm pretty sure Apple wouldn't switch the Macs to ARM chips if it wouldn't allow for major performance improvements. Or, if not "absolute" performance, then performance per Watt or price/performance - but if ARM proves to be worse than Intel on "raw performance", they will probably only switch the low-end models and keep e.g. the Mac Pro on x86 for now (or switch it from Intel to AMD, after all Intel is currently struggling to keep up with them). And I'm sure Adobe et al will happily optimize their software for ARM as well...