My opinion about autorouting was established many years ago…
All my PCBs (till now) are 2 layers. We use only SMD elements (electrolytic capacitors, terminal blocks and relays are really the only exceptions). Layout conception I use can be described as follows:
- use all bottom as GND,
- spend long time at element placement (and rotation) to find the best to make connections without crossing (I switch microcontroller pin assignment to functions many times),
- if can’t avoid crossing I prefere to add 0R 0603 then to break my GND at bottom.
- go with VCC (at top) under microcontroller and propagate from it radially (through corners and its VCC pins),
- put blocking capacitors just near each VCC/GND microcontroller pin pairs,
- put blocking capacitor for other ICs just near their VCC pin and via it directly to GND.