Lots of the newer-generation Chinese 11m rigs come with CTCSS standard. As mentioned, it provides zero actual privacy.
Your best bets are using a voice inversion scrambler (as mentioned), or using digital voice on 11m (26-28 MHz), VHF low band (30-50 MHz, but be careful what frequency you use in low band) or 66-88 MHz. I would caution against using certain bands within 66-88 MHz. Your best bets are probably 72-73 MHz and 74-74.9 MHz. Avoid 74.9 MHz - 75.1 MHz.
On 11 meters you could use AM or FM voice on the zeros. 11 meter export rigs default to 10 kHz steps (26.775 MHz, 26.785 MHz, 26.795 MHz, 27.455 MHz, 27.465 MHz, etc.) - going -5 kHz to the 26.770 MHz, 27.500 MHz, 27.650 MHz, etc. frequencies would reduce casual interception. I would avoid the popular 11m frequencies 26.285 MHz 26.555 MHz, 26.565 MHz, 26.585 MHz, 26.715 MHz, 26.725 MHz, 26.735 MHz, 26.775 MHz, 26.905 MHz, 26.915 MHz, 27.425 MHz, 27.475 MHz, 27.555 MHz and 27.635 MHz.
It is important to remember that 27.430 MHz, 27.450 MHz, 27.470 MHz and 27.490 MHz are actually land mobile FM business frequencies. There are only a few businesses who still use those channels, but they are out there. Most of them do use CTCSS/PL tones. 29.710 MHz, 29.730 MHz, 29.750 MHz, 29.770 MHz and 29.790 MHz are also allocated as business frequencies, and they are used in some areas.
As far as VHF low band goes, avoid the military/government only bands. The VHF business bands are relatively safe, but do a search for local licenses on your prospective frequency. The standard channel steps are 20 kHz (30.56 MHz, 30.58 MHz, 30.60 MHz, etc.) The business bands are:
30.560 MHz - 31.980 MHz
33.100 MHz - 33.400 MHz
35.020 MHz - 35.980 MHz
37.440 MHz - 37.880 MHz
42.960 MHz - 44.600 MHz
47.440 MHz - 49.580 MHz
Your safest bets are the itinerant frequencies and the 49 MHz Part 15 frequencies, which are allocated for users to use anywhere in the USA (as opposed to most licenses, which only authorize use of a specific frequency within a specific area).
The low band VHF itinerants are:
27.490 MHz
35.040 MHz
43.040 MHz
The frequencies in-between are used by public safety and military/government users. The military technically may use any frequency between 30.000 and 87.975 MHz.
The following bands are military/government only:
30.000 MHz - 30.550 MHz
32.000 MHz - 33.000 MHz
34.000 MHz - 35.000 MHz
36.000 MHz - 37.000 MHz
38.000 MHz - 39.000 MHz
40.000 MHz - 42.000 MHz
46.600 MHz - 47.000 MHz
49.600 MHz - 50.000 MHz
The 49.82 MHz to 49.98 MHz band is also used by Part 15 devices and is also a great place to "hide" with high power low band radios. The standard channels are:
49.830 MHz
49.845 MHz
49.860 MHz
49.875 MHz
49.890 MHz
The 49 MHz frequencies are largely abandoned for baby monitors/cordless phones/wireless intercoms in favor of the 1.9 MHz DECT band and the 900 MHz/2.4 GHz/5.0 GHz/5.8 GHz bands. There are some holdouts, however.
If you go the low band route, I recommend programming those five 49 MHz channels in, if only for short-range comms. There are preppers who include the 49 MHz channels in their handheld low band radios for short-range portable to portable communications. I have a set of Maxon PC-50 Part 15 portable radios that operate on the 49 MHz channels for very short range communications. There are situations where extra range is a bigger liability than advantage. Think "low probability of intercept". Same goes for the 100mw CB handhelds.
If you want to go the legit route, consider getting a Part 90 Land Mobile (Business Radio) license for one/several of the 27 MHz/29 MHz business frequencies and/or VHF low band business frequencies. VHF low band use is few and far between in many parts of the country and clear frequencies are often easy to find. There are militia groups that have gone this route.
Regardless of what you decide to do - do extensive monitoring of any prospective frequency. This includes 11 meter frequencies, low band and yes, the 66-88 MHz VHF mid band.