Mom diagnosed with Stage 4 lung cancer with Brain tumor

My mom(age 62) was diagnosed with stage 4 lung caner with a big tumor in the brain. She was having nausea/vomit symptoms for 2-3 months and finally an MRI of brain showed a cerebellum tumor. Since she had a seizure we got an emergency brain tumor removal surgery done. They also found multiple tumors in upper lobe of lung(3.6cm, 8mm, two 5mm and few 3mm) in lung and some lymph nodes is also compromised.
Tumor biopsy confirmed adenocarcinoma with primary tumor in lung. PD-L1 test was negative(<1%) which made me very very sad. EGFR and other gene mutation tests are pending. She is asian non-smoker female so good chance of EGFR positivity.
We were assigned to a community hospital(she has medi-cal public insurance in california) where there is no lung cancer specialist. The medical oncologist is a generalist who treats brain/lung/throat cancers.
Questions:
1) Mutation results from tumor testing are atleast two weeks out. Is there any point in seeing oncologist now or should we wait for full mutation result ? Its been 1.5 weeks since surgery and 2 weeks since diagnosis. Should we be rushing to start chemo treatment and switch to Osimertinib if EGFR positive or should we wait for full molecular testing ?
2) If no mutation comes positive and PD-L1 is negative also these are first line of treatments
->Pembrolizumab + (carboplatin or cisplatin) + pemetrexed (preferred)
-> Atezolizumab + carboplatin + paclitaxel + bevacizumab
-> Platinum-doublet chemotherapy ± bevacizumab
How does the doctor decide which one of these combinations is better for you ?
3) Is surgical or Stereotactic ablative radiotherapy (SABR), also known as stereotactic body radiation therapy (SBRT), an option for lung tumors ? Which one is recommended ?
4) Also we only did CT of abdomen and chest and MRI of brain upto this point. Does whole body PET add any value at this point or should we do it at the time of progression evaluation later ?
5) do you normally see a general medical oncologist or do you see a medical oncologist ? How important is the clinic/facility in the overall care for you ? I am asking because I can always get a second opinion from a top 10 cancer center and apply that plan at the local cancer center. This would save us a lot of long drives and expensive private insurance.