CGT on IP bought after budget, before 2027 Jul but later become owner occupied

We currently live in an owner occupied place.
Was gonna buy a bigger house as IP and rent it out for 3 years for NG and move in as primary residence after 3 years. But wasn’t able to find a suitable one before budget night.

So want to understand what’s the impact if I continue my search and plan and buy an IP in the next 1-2 months say, and rent it out (say still 3 years till 2029) and moved in, assume I live there for a further 12 years make the total ownership 15 years (3 years rented)
What’s the tax implications of this.

Understanding NG:
Between now and 2027 Jul 1, I can still NG against salary and wages.
2027 Jul to 2029 I can only only carry forward the rental losses and apply against future property income.

CGT:
Assume I got the house for 1.3m and sold it for 2m after 15 years. (3 years rented)
Under the old rule, it would have been 700k*0.2 =140 K for rented proportions, discount of 0.5*140k =70 K capital gain subject to tax based on my marginal tax rate that year.

Under the new rule slightly confused how it would be calculated. Do I have to get an evaluation on July 2027 to work out the accruals before that, and that portion is under the old rule. After 2027 Jul is the new rule?
How would the proportion calculate?

Since it’s indexation based. Would it be proportion of years doesn’t matter any more.
Obtain two valuation, one at 2027 Jul. one at 2029 before moving in.
Before July portion (old rule. 50% discount on gain)
2027-2029 portion (cpi indexation/30% min)

Assume a round number for calculating purpose
Say scenario #1
valuation was
2027 Jul: 1.35m
2029 before moving: 1.45m
CPI: 2% per year over 2 years

CG for tax will be (assume marginal tax rate > 30%)
50k * 0.5 =25 K
1.45m - 1.35m * 1.02 * 1.02 =0.0455 m = 45.5k
Total CG for tax: 25k+45.5k =70.5 K

Say scenario #2
valuation was
2027 Jul: 1.35m
2029 before moving: 1.45
CPI: 5% per year over 2 years

CG for tax will be (assume marginal tax rate > 30%)
50k * 0.5 =25 K
1.45 - 1.35m * 1.05 * 1.05 =-0.0384 m (-38.4K)
Total CG for tax: 25k -38.4K =-13.4 K
Carry a loss of -13.4K

Would this be correct or they will use the entire gain between 2027 to eventual sell (14 years) adjust CPI and proportion rented time for that period (2/14) for tax

Thanks.