I'd like to say this is my opinion, but there are many journalists more in the know than I am. It's interesting to see people crunch the testing numbers and try and get a pecking order as well as the relative gaps between teams. Here are two articles (plus a video at the bottom of the post) who have tried to predict the running order:
https://www.motorsportmagazine.com/opinion/f1/mph-ranking-f1-teams-heading-melbourne-updated
https://www.bbc.co.uk/sport/formula1/47423445
Both agree Ferrari are ahead, but by different margins, with Mercedes clear of Red Bull. Whilst Mercedes won on the laps done, Red Bull have done surprisingly few laps, and did not do a representative quick run due to Gasly's crash.
With the budgets at Renault and McLaren, there ought to be signs of them breaking away from the midfield this season, so it remains to be seen if the "B" teams (Alfa, Toro Rosso & Haas) manage to keep up with them.
It's not good reading for Williams at the back, but with their delays, and judging from Kubica's interviews, they didn't really get any time to put in some quick laps, so there's a bit of hope they aren't as far away as testing showed. However driver comments have been cautious at best.
The race at Melbourne, Australia is going to be an indicator of the pecking order, but it does throw up some strange results as it is a unique track. So it won't be until a couple of races in before it becomes clear where the teams truly stand.
I hope Ferrari isn't too far ahead. I hope Williams isn't too far behind. I hope DRS is not too strong.
