For the speed issue, need to see where they are used to know if it will affect things. Likely not at audio frequencies.
Higher voltage diodes can have higher forward voltage i.e. MUR320 (200PIV) 0.89V vs MUR330-360 (300-600PIV) 1.28V at 3A.
UF5402 is 200PIV 3A fast recovery 50nsec, Vf=0.9V 3A for the UF5400-5404, Vf=1.4V 3A for the UF5405-5408.
30DF2 is 200PIV 3A fast recovery 200nsec, C-16 case Vf=1.05V 3A