Ditto on much of what you posted. The $5 tickets seem to be the best value for one on a limited budget. Lots of $100 prizes, which is a nice win for a $5 ticket.
While statistically, the $20 games are better, it takes a lot more dough to play, and strings of losers are nearly as likely as the lower denomination tickets. I've had many $20 losers in a row - 6+ many times, and upwards of 10 once.
In PA, and likewise in many other states, since a handful of companies develop and supply tickets nationwide, regardless of the denomination, the vast majority of prizes are $1000 and less. Something high denomination instant players should keep in mind...
While the overall payout percentage in PA on instant tickets can be over 65%, the effective payout percentage when adjusting out larger (over $1000) prizes, which are few and far between, and break-even prizes, which are in huge abundance (winning $30 on a $30 ticket is better than losing, but still a letdown), the effective payout percentage drops somewhat, approaching that of number games.
For one seeking to win more than $1000, it's best to mix in some number games that have realistic odds, in particular, the Daily Number and Big-4.
With all that said, instant tickets are about to get better in PA next year. The 30% profit requirement on gaming revenue, which currently has been suspended on a temporary basis, has been indefinitely lifted allowing for higher payout percentages. Number games are likely to remain mostly unchanged, though will probably be more promotions. The big change will likely be 70% - 80% payout percentage for some instant games in 2015 - if this occurs, players will notice the difference - more playtime, and better prizes.