P0300, 0301, 0302, etc.

Gasket sealer? As in block sealer? Hope not.

All your symptoms are consistent with a Prius head gasket. Most report "no" coolant loss, various cylinder misfire codes, no codes early on but occasional cold start rattles and sometimes a thousand or more wasted on egrs, coils and plugs.

Once the issue is accepted the next concern should be warped parts, heads, blocks and rods. Warped heads are the most common issue, not cracked. If the block is warped it is done; the head should be professionally checked and rebuilt as necessary. Some independent shops have rebuilt heads and cleaned intakes/egr coolers ready to go to allow several "head gasket" jobs a day. Often the chain tensioner is changed since it is low cost and high consequence if it fails.

When you have progressed to white smoke, head gasket denial has gone too far to worry about a borescope. Be careful when evaluating your diy capabilities; some have done the job three times on the same car. Often the timing is off once or twice. One guy tore it down a couple of times before punting with a bent rod. He then upped the ante with a diy gen4 engine.